XP 64 had some issues. It now has many fewer issues, largly because driver support has caught up. I dont think there will be any Vista-only games for quite some time, I doubt there will even be much that uses DX10 for at least 2 years.There will be a couple pioneers of course, but im not seeing DX10 OS support as anything too important.

By the time people "really" want it, I think it will be time to upgrade again anyhow. In any case, cross that bridge when you come to it I say.

If your not getting a GF8800 DX10 card, no reason to get Vista in any case.