Well, I've be dabbling in the 32 vs. 64 bit area for some time now. I was on the XP 64bit beta test (and bought the upgrade) and also I have installed the 64 bit of Vista Business edition.
I don't see any benefits right now for 64 bit Windows Vista. The lack of driver and software vendor support is steering me away from the 64 bit versions for now. (no speed increases with any apps as far as I can see).
So right now I am running Vista Business 32bit and its working not to bad so far.
I think though during the weekend I will go back to Windows XP 32 bit.