Haveing used x64 Business since before its release, I can confirm that the drivers are definately up to a reasonable quality. The only x64 applications I run are Avast antivirus, mainly down to the fact that it uses drivers, which in turn must be x64 capable, and Far Cry x64 patch. As for x64 being any faster than x86 I can't really say for certain as I switched straight from XP Home to Vista x64 Business and although I noticed a considerable improvement in perfomance I cannot say for sure whether this was down to Vista itself or the x64 environment.
One thing I am certain of is that PatchGuard, a security implementation that disallows unsigned drivers from being applied to the kernel, is exclusive to all x64 versions of Vista only. In my opinion you shouldn't even consider x86 if you're making the switch to Vista. Although there aren't many x64 capable home applications at the moment, I feel you would still be better of with 64-bit. At the end of the day, you will at least have the flexibilty to run both 32-bit and 64-bit applications under x64 whilst with x86 you will be limited to 32-bit only. Couple those two points with the fact that you can use more than 4GB of RAM (up to 16GB for Premium and up to 128GB for Business and Ultimate) and the choice becomes a bit of a no-brainer.