I still use XP to, and ill be putting XP back on my i5 rig later tonight when ive built it, but it has to wait, been called out to install a router for someone.
windows 7 64bit is definitely much faster for me than XP 64bit was....
I think it handles the extra cores and ram better ?
(tho i turned off all the fancy gfx so it actually looks like xp)
something to think about