Only? hardly, games that work fine on xp have to be hacked up (usually)
I've had close to 100 games and demos installed and yet to find one that was less than perfect.
(for example, assassins creed didn't even install on vista in a tech demo for IGN - which means more development time)
The best example you can come up with is a beta version given to the media that doesn't involve you at all? Figures. Most of the people who claim to know most about Vista's problems have no personal experience.
AND it requires dx10 gfx cards
No, it doesn't.
And simply this: its slow.
Again, presumably not talking from personal experience. I find it much faster than XP, which was no slouch itself. It's far, far more responsive.