Just a couple of months ago, in this column, we proclaimed that Apple Computer’s iMac G5, then the company’s flagship Macintosh desktop computer for consumers, was the best consumer desktop PC on the market. In fact, we called it the “gold standard” of desktop PCs and said no desktop from the major makers of Windows-based computers could match it.

Last week, in a surprise move, Apple gave the iMac a brain transplant. It chose the iMac as the first Macintosh model to be converted to work on the same Intel processors used by makers of Windows PCs, rather than the PowerPC processors from IBM that have powered Macs for many years. This was serious surgery to perform on the company’s star product and launched the planned transition to Intel much sooner than originally expected.

Apple’s new Intel-powered iMac.

Apple says it changed chips because Intel’s latest processors are faster and run cooler, and allow for more flexible and creative computer designs in the future. It says the new iMac is two to three times as fast as the old one, mainly because the Intel Core Duo chip it uses packs in the equivalent of two processors.

But there’s a downside. Nearly all existing third-party software for the Mac, including major programs like Microsoft Office, will have to be rewritten to run on the Intel processor — a process that is under way but will take months to complete. Apple had to build into the new model special, invisible, translator software that allows the older programs to run on the new chip in the meantime. This translator software, however, doesn’t work with every program and can slow down the ones it does work with.

So, how did the brain transplant go? Is the new Intel iMac as good as its predecessor? Does the machine’s raw power offset the translation slowdown?

To find out, we’ve been testing an Intel-based iMac against an iMac G5 only about a month old. The two machines look identical and sport nearly identical features. The major differences are hidden under the hood.

For days, we ran a wide variety of software on the two iMacs, and performed all of the common tasks mainstream consumers do — surfing the Web, emailing, instant messaging, word processing, using spreadsheets, editing photos, playing music, managing personal finances, playing simple games.

Our verdict: The brain transplant was a success. The two machines behaved almost identically in our tests. Compatibility is excellent. The new model easily handled all the major consumer software we threw at it. We never noticed the translator software, called Rosetta, and any slowdowns it imposed were so slight as to be indiscernible.

The new model was actually a little faster at a few of the tasks we tried, but nothing like the two to three times as fast that Apple claims. A mainstream user who didn’t know what was under the hood couldn’t tell the difference between them, even after using them for hours. It appears that the faster chip roughly balances out the translation effect.

So, if the new model works only about as well as the old one, what’s the advantage for consumers? Well, the slight, scattered, speed gains we saw should grow greater over time, as Apple and third-party software makers tweak their applications to take full advantage of the dual-core Intel chip. A year from now, an Intel iMac purchased today will likely be notably faster, if you update your software to newer versions.

But, even now, this is a terrific computer. It’s still the best consumer desktop on the market. It still runs crisply, still is free of viruses and spyware, still has the best operating system and the best built-in software of any desktop we’ve tested. Given how smoothly the new machine works, and how likely it is to get even better, we would prefer it today over the iMac G5, which Apple is still selling for the same price until inventories are gone. The G5 is still a fine machine, but the Intel model has a brighter future, and, based on our tests, it seems ready to go today.

There are a couple of caveats about our results. We tested only common consumer software and tasks, not heavy-duty or professional applications, like Adobe Photoshop, or professional music and video programs, which tend to stress the processor. Some of these nonconsumer products won’t work right until they are rewritten.

Also, there are two drawbacks to the Intel-based iMac that we judged relatively unimportant to most users, but which could be crucial to some. It can’t run old, pre-2001 Mac programs that were written for the old Mac operating system, called “Classic.” And, even though it now uses the same processors that Windows machines do, the new iMac can’t run Virtual PC, the Microsoft program that allows Macs to run Windows software. Microsoft is rewriting Virtual PC for the new Macs but won’t be done until 2007. Some other company may bring out a way to run Windows stuff on the new Mac sooner than that. But, for now, it can’t run Windows programs.

On the other hand, the new iMac has a few advantages. It has a faster video card than the old model and a digital video connector rather than an analog connector.

Doom 3, a non-Apple program, ran well on the new iMac.

From the outside, the two machines are twins. Apple was careful to keep the same physical design, a beautiful white flat-panel monitor with the entire guts of the computer stashed behind the screen in an amazingly thin space. Both have a built-in camera and microphone. The user interface and software features are also identical. Both models run the same excellent Mac OS X operating system. And both also include Front Row, the special interface that allows you to view photos and videos, and play music, from across a room using a small, included remote control.

Even the price of the new model is the same — $1,299 for a version with a 17-inch screen and $1,699 for one with a 20-inch screen.

For our tests, we copied all the third-party software and files from our iMac G5 to the Intel iMac, so the machines were configured comparably. Both had the same amount of memory, the same DVD drives and the same Internet connections.

We ran a mix of Apple and third-party software. We weren’t surprised that all the Apple programs, like iTunes and iPhoto and the Safari Web browser, ran perfectly and swiftly. Apple has already rewritten them for the Intel chip.

But we were pleasantly surprised by the performance of non-Apple programs. We tested Microsoft Office, Adobe Reader, the Firefox Web browser, Skype, Google Earth, Quicken, the Eudora email program, Doom 3, Kodak EasyShare and others — none of which had been rewritten. All launched quickly and ran smoothly and well.

We did find one program that wouldn’t run at all on the Intel iMac: AOL for Mac OSX. But AOL’s main features can all now be accessed from its Web site, so you don’t need this software in most cases.

Web pages loaded swiftly on the new iMac, though not markedly faster than on the old model. We changed the font on a thousand-word document in Microsoft Word and saw no lag at all. We created a chart in Microsoft Excel, and it appeared almost instantly. Email worked indistinguishably well.

This column was written in Word on the Intel iMac, and there were no glitches or hitches or hang-ups of any kind.

On four of our test tasks, the new model outperformed the old one significantly — all in Apple software that had been rewritten for the new chip. It was 15% faster at importing music from a CD, using iTunes. It was 42% faster at converting a video clip from one format to another, using Apple’s QuickTime program. It was 44% faster at importing nine large digital photos into iPhoto. And it was 24% faster at duplicating a huge folder filled with more than 27,000 files occupying more than 12 gigabytes of space.

Why didn’t our results support Apple’s claim of a two to three times speed gain? Like most computer companies, Apple bases such claims on special, complicated benchmark software that doesn’t necessarily match up with the kinds of mainstream consumer tasks we tested.

The bottom line: Apple’s iMac, with its new Intel processor, is still the gold standard of consumer desktop PCs. And it stands to get better over time.

• Email: MossbergSolution@wsj.com.

So my decision to abandon my old — yet reliable — Lotus Organizer software was a difficult one. But two serious issues prompted my switch: accessibility and flexibility. I use multiple computers in my office, my home and on the road — a mixed bag of Windows PCs and Apple Macintosh models — and I needed a calendar that I could access from every one. I also needed one that would allow both me and my assistant to update my calendar and instantly see the results.

For many people working in large organizations, with Microsoft Outlook or other calendars on servers, this is already a reality. But for consumers and small businesses, it’s a hassle. It’s a pain to keep updating calendar programs that live on multiple computers, even if you only use one type of computer, and even with the help of a PDA or smart phone, like my Palm Treo. And it gets far worse if you use both Windows PCs and Macs, or if you’d like to occasionally rely on public computers or borrowed computers on the road.

But there’s new hope in this area. Web-based calendars, which live on the Internet and can be accessed from any Web-connected computer, are getting much more powerful and sophisticated.

AirSet by Airena Inc.

So, for the past three months, my assistant Katie Boehret and I have been testing two Web-based organizer programs to see which one would replace Lotus. We tested a free organizer called AirSet by Airena Inc., as well as a $39.95 per year (after a free two-month trial) program called Trumba OneCalendar by Trumba Corp.

Each company set us up with our own password-protected calendars, and we quickly learned a few things. Because of the Internet’s nature, we had to adjust to waiting a bit for Web pages to load before performing tasks such as viewing future months or dates to add appointments. The Web also prevented us from simply dragging and dropping appointments from one calendar square to another, like we did in Lotus. And of course, when the Internet isn’t available, neither is my schedule.

Trumba is primarily a calendar, while AirSet is a broader service that includes a rich address book, automatic map links to meeting locations and a coming program that will work with mobile phones to access and update your calendar.

But we focused on the calendar features in each, as calendars are the most heavily used feature in most people’s computer organizers. We didn’t pick a winner because tastes in calendars can vary with work style. For us Trumba was better and easier, but for you, it might be AirSet. Both work well.

If you’re hoping to transfer your currently used calendar over to either of these, both programs will automatically synchronize with Microsoft Outlook, and AirSet also syncs with Palm Desktop. But any other type of calendar can only be moved using a special file format and it won’t synchronize perfectly.

Both programs also allow you to “publish,” or share, your calendar with other people, using different colors to represent each colleague or family member. And each allows you to “subscribe” to other people’s calendars, or to public calendars, like sports team or school schedules. The dates on such calendars are added to your own, and can be turned on or off.

Trumba OneCalendar by Trumba Corp.

The two programs are similar in many ways, but a few differences stood out to us. For one thing, we liked the overall look of Trumba better than AirSet. Its colors and the Web-page design are simple and attractive.

We also noticed a few small organizational distinctions. For example, my calendar’s appointments are organized by times (12 p.m. lunch with rock star, 2 p.m. meeting with tech legend) while some people and families have weekly activities and don’t need to know times — just that the activity falls on a certain day. Trumba lists an appointment or activity’s time first, while AirSet may list the time or activity first (Soccer Practice 2 p.m., Piano 4 p.m.) depending on how much data you enter in an appointment. We prefer Trumba’s method, but this is a personal inclination.

I started off with AirSet, quickly setting up a group named Walt’s Office. Groups help you distinguish schedules — such as personal and professional — from one another. Each group is labeled with a different color; AirSet automatically assigns colors to groups while Trumba lets you pick each group’s representative color from 24 shades.

I gave Katie permission to view and change the content in my AirSet calendar, and both she and I were able to view these changes, as long as we refreshed the page on each of our computers. Tabs labeled with your group names run across the top of AirSet, and you can easily switch from one group to another by clicking on each tab. One condensed tab shows you all of the groups’ activities in one calendar.

We entered the Subject, Location and Address into our AirSet appointments after selecting a “New” link in the appropriate date box. When we entered specific address information, a “Map It” link appeared beside the address and we could click on it to be directed to Google Maps and a geographical view of the meeting spot. This feature would probably be handy for professionals who drive to new meetings often rather than parents who are more familiar with neighborhoods and locations for activities.

Next month, AirSet will offer another attractive feature for small businesses — Mobile AirSet. This is a miniversion of the program that will sync data from your cellphone to the Web site and vice versa using your cellphone’s Internet service. We tested this using a demonstration phone from the company, and calendar events were pretty simple to open and change by pressing a few buttons on the phone. This service from AirSet will cost about five dollars per month.

AirSet imports contacts from Microsoft Outlook or Palm Desktop, including names, phone number, Web sites and emails. Trumba, on the other hand, only lets you import lists of email addresses.

Trumba’s groups run down the left-hand side of your calendar in list format, labeled “Your Primary Calendar,” “Shared With You,” “Emailed to You” and “Subscribed To.” Katie accesses four Trumba calendars daily: my office calendar, her personal calendar, my personal calendar and a free public calendar that she subscribes to called U.S. Holidays.

A small box aside each calendar name can be check-marked when you want to view that group’s activities — if you’re given permission — merged with your own calendar. This means you can view a variety of combinations of groups rather than just all of the groups’ appointments at once.

Reminder emails for appointments can be set up on both programs, which we did easily. AirSet emailed us daily reminders of the next day’s schedule every evening at the same time. Currently, AirSet and Trumba offer to send free reminders to your cellphone using text messaging, and AirSet can also send free daily schedule summaries using the same method.

If you want to publish all or just one of your Trumba calendars on the Web, so others can view them, you can do so using a five-step publishing wizard. Katie and I each did this very easily in just a few minutes, making sure to keep my calendar password-protected as we published it online. Publishing might come in handy for sports teams, clubs or work-related appointments — allowing everyone to view and/or subscribe to your calendar’s Web page.

AirSet’s Web-publishing process is more complicated for the average user, including instructions on how to cut and paste HTML code to give you — and anyone you give permission — access to your calendar on the Web.

Whether you’re more tech savvy and like some of AirSet’s richer features or you just like the straightforward approach of Trumba OneCalendar, you’ll almost certainly find it advantageous to keep various schedules and calendars organized together in one easy-to-access Web-based calendar. Both programs are free to start, so it might be worthwhile to schedule some time for testing these two organizers.

With reporting by Katherine Boehret

• Email me at mossberg@wsj.com