All systems I setup now are x64 win7.
Personally I am running 8gig of ram, but that's for dealing with playing with my dev tools and modeling work. I have to say it would be a giggle to try multibox WoW now that I have quad core and all that ram and a new video card (GTX275).
Before I was running a 7900 and a dual core with 2gig of ram, the difference can be felt now as I can run pretty much anything in the highest of settings.
Just seeing the stats is awesome from a development point of view, knowing what customers have capability wise and being able to target who you want. I'd like to see those with DX10 cards and win XP moving to Windows 7 and we might finally be moving to DX10 min requirement (DX11 is very nice, but at least getting to DX10 would be a start).
Then again DX9 is doing it's job nicely considering it's age, it would be nice to skip DX10 support and go straight to D11, which looks likely in the next year or so.