My gaming pc runs windows 8. I don't like 8 much, but it's been just fine for gaming.
Same here; I upgraded for X-Com. I chose Windows 8 because it's a lot cheaper.
And I don't know if this is objectively true, but I do feel that a lot of programs (Steam especially) and games run A LOT faster on Win8 than on WinXP.
I would expect this to be true. we're talking three major os versions difference, not to mention moving from 32 bit to 64 bit, most likely.
I'm sticking with 7. I satisfied all of my curiosity about 8 through the job and I won't be upgrading until the games and the directx version starts to impact what I can play. Not a fan of the metro interface and unless I can kill it completely, I'll happily avoid upgrading.