You'll find that most cpu's these days have the 64 bit command set and most people are chomping at the bit to use more than 3.5 gigs of ram (old XP limitation). Windows 7 will primarily be 64 bit I'm guessing since a) most cpus for the last 4 years can do 64 bit and b) people really really want to use loads of RAM, esp with the new i7 platform having 3 way memory (3x2 is what Im getting, will have the option to get another 3x2 for the other 3 slots - 12gigs entry level is phenomenal...
The only driver issues I can imagine are older hardware and certain USB devices. Logitech has been notoriously shithouse for 64 drivers before but I'm interested to see how they treat their customers once W7 is out (I have logitech mice, kb, speakers, joystick, webcam etc - excellent hardware but the driver support (used to) leave a lot to be desired..)
Im really looking forward to this new system. has been 5 years since I upgraded - I'm rather proud of that, and my AMD3200/1gb/36gb raptor will make a sweeet linux box
oh and ive managed to scrounge a dds drive out of spare bits so I has me a tape backup unit too
Going for a cheap vidcard atm since all I play is world of warcraft and that should do it easily... will get a dual SLI beast later on when the next hardcore 3d shooter gets released no doubt hehe
-D