As far as I'm concerned Apple has already won.
As with many here I've used both platforms for years, watched them develop. I always felt more productive on a Mac (Photoshop, Illustrator, Dreamweaver, BBEdit, etc.). But I've watched Windows go from 3.1 to 95, to 98 and in the meantime, Mac OS wasn't upping the ante much in the transition from 7 to 7.5 to 8 to 8.5 to 9. I was really worried about Apple's future, but I figured the worst thing that could happen would be I would have to switch to Windows. That wouldn't be all bad, after all, I can get my work done nearly as quickly on Windows.
Now, however, my enthusiasm about Apple is at an all-time high. Not only is Apple doing better than any other computer manufacturer this year, but Mac OS X finally lets me leave behind my anxiety about investing in a non-Windows platform. I no longer care if Apple gains market share, because with the transition to a BSD-based OS and other standards like PDF, I no longer sit in the lonely Mac-world where I have to depend on Mac Developers or even Apple to release what I need. Now I'm sitting in the unix, open-source world, where if I really need something done I can do it myself, and better yet, start an open-source project for all Mac OS X users.
It's mostly a moot point, however, since as a web developer, OS X has already met my needs perfectly. Running Apache w/ PHP & MySQL next to Photoshop, Dreamweaver & BBEdit has increased my productivity by a solid 10%, not to mention the benefits of being able to test code upgrades without renaming PHP files and such.
At this point I couldn't care less about XP. XP could have dozens of cool new features, a great new interface, be easier to use than Mac OS X. I wouldn't care. I just sit back and smile at the beauty of Apple's GUI on a true network platform... 10.1 can only be better...