Besides for the MBP drivers only being 32bit. A vast majority of software for Vista does not support 64bit.
Currrent drivers are 32-bit, but frankly the 64-bit version of Vista doesn't make much sense anyhow - a lot of software and drivers are broken AAAAAND it's slower in day-to-day use.
What are you saying, that the majority of programs aren't written in 64-bit, or that the majority of programs don't run on the 64-bit version of Vista?
Vista x64 doesn't have any problems running 32-bit apps...as others have said, the only benefit today would be to be able to use 4GB+ of ram.
4) There have been many benchmarks already, so who ever is screaming fud whilst foaming at the mouth needs to look at the benchmarks. There is little advantage above greater memory addressing; even then, with the extra weight, you need more memory to run it.
Software isn't slowed down, I don't know where you heard this. It's also not any more slower than a 32-bit OS.
Currrent drivers are 32-bit, but frankly the 64-bit version of Vista doesn't make much sense anyhow - a lot of software and drivers are broken AAAAAND it's slower in day-to-day use.
3) Who ever raised the 3GB, bull rot. The issue regarding 3GB is the chipset limitation - also, the issue is 4GB combined memory, when Windows looks at the memory, it combines video memory and ram together. In the case of a MacBook, its a non-issue as the graphics memory and RAM are one in the same.