The extraordinary thing about Apple's new iMac is how ordinary it is to operate. It looks, sounds and works almost exactly like the version it replaces, to the point where many Mac users probably couldn't pick it out of a lineup. But the iMac's strikingly stylish contours hide an Intel Core Duo processor, not the usual PowerPC chip. It's the first Mac ever to show up in stores with Intel inside. Most computer companies switch processor architectures only a little more often than human beings switch heads, and with good reason. Apple had done it only once in the past 20 years, when it moved to PowerPC chips in the mid-1990s -- a prolonged, painful process with its own vocabulary of system-error messages -- and Microsoft has yet to attempt it with any consumer flavor of Windows. The new iMac, however, makes this sort of brain surgery seem Band-Aid easy. With Intel-fluent Mac software-- a small but growing contingent that includes the Mac OS X operating system and every Apple program on board-- this computer barrels past the iMac G5 it replaces. But the new iMac can also run older, PowerPC software at a large fraction of its original speed, and with no sacrifice of features. The Intel iMac Apple loaned last week (the pricier of two versions, this $1,699 model includes a 2 GHZ Core Duo and a gigabyte of memory) looked its very best in tests of digital-video performance. It played high-definition movie trailers available on Apple's Web site without pauses or stutters, even when I rapidly dragged the movie's window around the desktop. An iMac G5 from last summer stumbled, sometimes badly, at the same assignment, as did a Dell Optiplex desktop. Then I tried copying a DVD movie to the hard drive and compressing its footage to play on a video iPod. An Intel-compatible release of the program I used, a free download called HandBrake, finished everything in an hour and 19 minutes; a PowerPC version needed over two hours on the fastest iMac G5 sold. The same snappy performance showed up in many other Intel-ready applications, such as the iLife '06 multimedia suite bundled with the iMac. But most Mac programs aren't yet available as "universal" Intel/PowerPC releases. In those cases, the iMac and such other Intel-based machines as the MacBook Pro laptop due next month rely on a layer of software called Rosetta to translate PowerPC code into Intel instructions. Much of the time, Rosetta is invisible. Microsoft Office launched only a little slower than normal, then acted exactly as it would on a G4 or G5 Mac. The same went for a long list of other Mac programs tested, including productivity applications (AppleWorks), personal-finance tools (Quicken 2006, TurboTax, Moneydance), Web browsers (Firefox and Camino), digital-photo managers (Kodak EasyShare, iView Media) and games (The Sims, Lego Star Wars). A Hewlett-Packard printer/scanner combo worked as usual, and I had no problem installing drivers for comparable devices from HP and Epson. Rosetta even tolerated the quirks of gruesomely obsolete Mac software: Palm Desktop synced data with a Tungsten E handheld and AOL logged on over my DSL connection without any issues. Rosetta could not, however, run demos of the games WWII Online and Doom 3 at any acceptable speed. LimeWire, a file-sharing program, and NeoOffice, a version of the OpenOffice suite, wouldn't start or crashed every time. Microsoft's Virtual PC emulation software doesn't work either. And Rosetta can't translate any "Classic" programs written for Mac OS 9 or older versions of Apple's operating system; Mac OS X actually stamps their icons with a "forbidden" graphic to emphasize this point. Even with those glitches, Rosetta (developed for Apple by Silicon Valley start-up Transitive Corp.) stands as one of the most amazing feats of emulation I've seen. Its only major cost seems to be a ravenous appetite for memory: Rosetta often wound up doubling PowerPC applications' memory requirements, a trait that made the iMac unbearably sluggish with one of its two memory modules removed. Don't even think of using an Intel-based Mac without a gigabyte of memory on board, not the 512 MB that would suffice on other models. Although the Intel Core Duo chip in the iMac will also soon grace many Windows laptops, other parts of this Apple's innards aren't compatible with Windows XP, at least for now. (Using this laptop processor offers the utterly pleasant side effect of making the iMac almost silent in use.) But that should not stop owners of Intel-based Macs from running Windows programs on their machines. For one thing, Microsoft says it's researching how to update Virtual PC for them. For another, Mac versions of Wine and CrossOver Office -- programs that for years have allowed Linux users to run Windows programs without even installing Windows itself -- have a good chance of arriving before Microsoft can ship a universal version of Virtual PC. (In case you were wondering, Windows viruses also don't have any access to these computers.) Both the promise and the reality of the Intel iMac -- especially the cheaper, $1,299 model, once upgraded to a gigabyte of memory -- make it one of Apple's most appealing releases ever. But it would still be wise to wait a month or so if you don't need a new machine today. This computer may look just like its predecessor, down to the too-few USB ports on the back, the slot-loading DVD- and CD-burning "SuperDrive" on the side, and the iSight webcam above its fabulously bright screen, but it represents an enormous change inside. And in the computer business, enormous changes usually mean lots of bugs that don't surface until after a product lands on store shelves. Waiting a little will give Apple time to find and fix those bugs, then work on taking better advantage of Intel processors. It will give the developers of Mac software time to rewrite more programs as universal releases -- or at least make sure that their current releases function correctly under Rosetta. It's barely been six months since Apple even announced that it would move to Intel processors. Waiting a little longer won't hurt and could save you a lot of trouble.