Just a comment expanding on those already put; although Vista, with proper(High) Hardware requirements met, there is a need if your a hardcore gamer to play pre- Dx 10 games so you may want to have a WinXP PC handy, or Dual Boot with Vista, probably not such a great moment to do so with Win 7 just around the corner
Win 7 will add more options too ..., i.e. the addition of WinXP within a Virtual machine which may in fact make the Windows 7 option better than Vista.
Just a thought, or a couple of questions, I'm not a gamer