From a gaming point of view, eh?
How about bad support for Sli and Crossfire? How about the fact that there are DirecX10 games that perform worse when using Vista and the new DirecX? The list goes on and on. Honestly, even a game like Crysis will be gorgeous using the DirecX9 API. It\'s not near the end of it\'s life.
With that said, go ahead and get Vista and a GOOD DirecX10 card. No sense in not future-proofing yourself, even if it\'s not needed now.