Apple with Intel Inside - The Beginning
Okay, Apple has rolled out the first two Intel-based Macs (and I've got a MacBook Pro -- that name's gonna take some getting used to -- configured in my shopping cart), but some of the real fun hasn't started yet.
Watch for solutions to run Windows Apps on Mac OS X
As Andy Ihnatko pointed out way back in June, you know somebody will devise a way to run Windows apps under OS X.
It could be a solution along the lines of VirtualPC or its predecessor, SoftPC. Although Microsoft acquired and now sells VirtualPC, both of these products were spawned from relatively small development efforts, and the technical challenge was much greater than it is now: both of these products had to run Intel binaries on non-Intel CPUs (the 680x0 and later the PowerPC). It will be much easier to build a solution where the code can run natively, not to mention much faster.
Another approach is Darwine, which is a derivative of Wine. Wine enables (many) Windows application binaries to run under Linux on x86 architectures by implementing Windows APIs. It avoids the processor emulation challenge, although I would think that keeping up with Redmond's creation of new APIs isn't all that easy, either. Most notable about Wine is that it does not require a Windows license to run Windows apps.
Darwine started out as a port of Wine to Darwin, the open source Unix foundation of Mac OS X. The project was challenged by the architectural differences between Linux and Darwin/Unix, as well as the processor emulation problem that Wine does not address. With the introduction of Intel-based Macs, some of that challenge goes away.
And, of course, there's always the option of dual-booting Macs into OS X and Windows. Unwieldy, but it may be sufficient for some people.
Oh, and then there's the possibility of buyying an iMac or MacBook just to run Windows, without OS X. There's precedent for this: a fair number of Linux users run it on Apple hardware.
A bigger market for Apple hardware
The upshot of these new possibilities, in my opinion, is that Apple has a potentially larger customer base for its hardware. The Mac loyalists should remain in the Apple fold, especially if Apple is successful in keeping OS X from running on non-Apple hardware, and there seems to be a "switcher" trend underway, perhaps from the "iPod halo effect". The new potential customers are those who are tied to Windows, but for whom the possibility of having enough access to Windows will be sufficient to get them to consider Apple hardware.
This could be huge for Apple. Let's stipulate that the sales rate for the desktop/laptop market is 95% Windows and 3% Mac. If only 1% of those Windows users buy Apple hardware, that's roughly a 30% increase in the sales rate for Apple hardware. Apple is already healthily profitable at current sales levels; any additional growth is financial gravy.
I'm sure Apple would prefer that people run OS X, but it can't hurt to get some revenue from the Windows base, and a Mac hardware/Windows software user is one (big) step closer to becoming an OS X user.
Apple and Microsoft
Lost in the noise here is the announcement of a five-year "agreement" between Apple and Microsoft wherein Microsoft has committed to continue developing Office for the Mac platform for five more years. This puts to rest the notion that Apple's move into the Intel space would alienate Microsoft and threaten Office support. This little bit of uncertainty about the Mac platform is put to rest for a while.
The unanswered (and so far unasked, as far as I can tell) is: what did Apple agree to in exchange for Microsoft's commitment? There are all sorts of possibilities, like a side deal over music and/or DRM, but I'll keep my guesses closer to home. Maybe an agreement not to develop a competitor for Office (the rumored "Numbers" application for iWork)? Or maybe to stay away from actively supporting OpenOffice? I don't know, but there has to be something, and I'd love to know what Microsoft thought they needed (or wanted) from Apple...