I can play every new and old game I have on Vista 64.
However, most games still run a little faster on XP 32. (Even with the 3 gig limitation).
So, it may be until after Windows-7 that 64bit software finally shows improvements over XP.
Windows 7 will also better use quad-core CPUs.
Like others said, you should have 4+ gigs when using a 64bit OS. Not sure about the 1 gig video card in 64bit - but makes sense.
I got Vista 64 Ultimate to try to get an easy upgrade to Windows-7 64bit. Don't know yet if that was smart or stupid.
However, for things like RAID5, XP requires loading specific drivers, etc. Vista 64 just saw it and automatically loaded it.