I"m trying to figure out whether I need to go with the 64-bit version of Windows 7. I'd rather not unless there's a big benefit just because one or two missing 64-bit drivers (or one app that doesn't work quite right wold be a lot of work).
Biggest reason to go with the 64-bit Windows 7 (that I can see) is letting you use more RAM. But I never max out my RAM now (despite simultaneously burning CDs, testing sw in Virtual PC (Windows 7 no less) and editing something in Microsoft Word).
Since Windows 7 has a minimum RAM of 1 GB (vs something like 64 MB for XP) that suggests that Windows 7 uses a LOT more RAM.