MJM, until 64-bit apps are developed, it is true that there is no reall speed improvement AND there is memory waste. It was true when coding transitioned from 16-bit to 32-bit.
Basically, think of a a 64-bit data word being used to transfer a 32-bit word. Half of the data word is empty and not used. And, to save code as a file will be the same thing... A 32k word will be saved as a 64k word. And, that goes for RAM, as well as HDD.
It is when the new software gets released in 64-bit optimized form that the 64-bit processors will shine. Right now, only XP-64 is taking advantage of it. Linux and Unix already does. But, when apps we relate to (Nuendo, Reason, Sonar, Audition, ProTools, etc.) come out in 64-bit, we will all be pleased.