I've never had Vista anything. ATM I have WinXP x64 on a Q6600 G0 desktop and WinXP x32 on an older 1.73 Ghz Dell D610 laptop. I have Win7 x64 on another Q6600 G0 and Win7 x32 on an ancient 1.8 Ghz nc6000 laptop (easy breezy install, everything recognized outa' the box). The Q6600's have 8 GB's DDR2 PC 6400 RAM and the Dell D610 has 2x GB's of DDR2 533 RAM. The nc6000 laptop only has 768 MB's of DDR1 PC 2700 RAM.
Both Q6600's are water cooled and pretty much identical (same clock, same amount and type of RAM, etc). The D610 is 1.73 GHz and the nc6000 is 1.8 Ghz. The nc6000 has a Intel 855PM chip set mobo (Carmel) and the D610 has a Intel 915GM chipset mobo (Sonoma), so my observations are probably skewed and inaccurate (just real world, no scientific measurements).
In my humble opinion the older nc6000 is much more responsive now. The nc6000 had WinXP x32 Home on it previously and I had sound driver problems when I first installed the XP, with Win7, I had no problems at all, Win7 recognized everything right outa' the box

I don't see much difference in the two Q6600 G0's (one had WinXP x32 and the other still has WinXP x64) . Both were DCing 24/7 before the summer heat made ACing and DCing too expensive (AC' electric bill). They both got about equal results DCing

When my pre orders come I'll install Win7 x32 on my D610 and see if I think I see any noticeable improvement. I'm gonna' keep WinXP x64 on one Q6600 G0 and replace the Win7 x64 RC with the Win7 x64 GA on the other Q6600 G0 when I get it.