I have 2 Windows installed. XP 32 bit and Vista 64 bit where all of my 8GB mem are available.
But I spend 95% of my time in XP. Why? Because of shitty driver support and lack or 64 bit apps. My gfx board tend to "disable" direct X thingies, but I'm pretty lucky. It snaps back on in a sec or two later, while I've read that some have to wait much much longer, and there are others who are forced to restart the computer.
My beloved Audigy soundboard is supporded - but since I'm using 5.1 headphones and Creative Labs are whores, I can't use my headphones in stereo mode. Well, Ok... a dude hacked the drivers so it is possible, but the hack is kinda buggy and sound quality suffers.
There's even lack of 32 bit software capable of running on Vista 64 - and also lack of
propper functioning apps. Apps which are officially reported as being able to run on Vista 64 (some features gets disabled - sucky for me as these are the ones I prioritize the most.. doh!).
It was a big disappointment to me - however, I do 3D stuff and my 3D app is in 64 bit.. so I do get
some use out of it
Would I recommend 64 bit? Nope... but then again - I expect my system to work flawlessly.