1) im not an expert nor am i a geek, though im a wannabe, 2) i believe future applications will use 64 bit encoding, however this will be better actualized in the next intel chip, the rosetta, 3) and near future software will allow 32 bit so dont worry aboot system requirements, 4) 64 bit might run fractionally cooler and might have an effect on speed (refer to point #1) in future applications that use 64 bit.
Great notebook! and finally I can install windows (I know - i know, not the best but I need it) with bootcamp.. tried to install SP1 to than install SP2 over it but it just crashed, etc. so I'm doing that slipstream business.. what a pain, honestly.