I'm a bit confused as well. Compatible as in I can transfer my MS Word or JPEG or Photoshop files from Windows to Mac? Sure, I can do that. Compatible in that I can connect my Mac to a Windows server and see all the files? Sure, I can do that. Without modifying the Windows server too. Compatible in that filenames on the Mac have to have the Windows 3-char filename extensions? Sure, OS X forces that on Mac users now too. :|:|:|
Or compatible in that I can run Windows executables on Mac? Hmm...that would be interesting. But then the Mac would probably have to give up all it's metadata and other advanced features (oops, OS X already has done that.) And Apple can't even get complete compatibility with their own legacy apps in the transition from the classic Mac OS to the new OS X.
Compatible in that OS X (not just the Darwin core) can run on x86 hardware? That could be cool, but Apple can't even make OS X fully compatible with their own hardware. They can't even get hardware acceleration running on older Rage II/Pro integrated video chipsets on supposedly "OS X compatible" hardware. Nor will USB CDRW drives that worked with OS 9 ever work with OS X, nor OEM SCSI cards included in Macs, etc, etc... If they can't do that, how are they supposed to support the multitude of chipsets/mobos/drives/cards/etc that are commonplace in the PC world?
I loved the Mac, and used it since it was introduced. But it is a niche platform, now more than ever. And OS X is so unfinished it's laughable. It's like working with an early beta release of Win2k. You can see a lot of potential, but it's so far from useable it's pathetic. Heck, Win2k was still having hardware driver issues for over a year after it was released. How long will the Mac with less than 5% marketshare take to get decent hardware support? Try never.