64 bit is to 32 bit what 32 bit was to 16 .
Its a huge difference in gaming performance, and visual effects with other programs, its increased colour depth, and loads more raw data can be processed by the cpu, remember 16 bit games at all, l still have one, my 4400+ dual core AMD can run it fine, alot of older games wont run on xp or 64 bit cpu's or dual cores even, my 16 bit pc game is battlezone, given it pretty old now, when you see the graphic difference between them old games and todays, like say, Half Life 2, there is no comparison, 32 bit owns 16, and 64 bit will OWN 32 bit, just a matter of time now.
Bring on 64 bit, and physic's for that matter !