I get a free upgrade to windows 7 because of my newer laptop. I have the 64 bit Vista now and I hope to be able to downgrade to the 32 bit windows 7 because I've been having a lot of compatibility issues. For instance I can't get Primavera 3 to work right now due to it being a 16 bit program. My version of P3 was free due to school but i looked up the problem at a few different websites and their recommendation was to just purchase a newer version
FWIW, I've been running 64bit since XP. I had driver issues with XP64 but that was just because there were very few made for the x64 platform back then.
Currently, I'm running W7 64bit with an Athlon CPU. I've never had performance issues while running XP64, Vista64 or now 7/64.
I do try to use the 64bit versions of any software I can. Seems developers are upgrading pretty often. I'd say right now on my puter, it's about 50/50 with 32 to 64 bit programs.