I have 300gb of music I dumped the database when I went to 4.0 and it is reimporting, it is up to 70K songs.
It is using 3-4-5% cpu and 361 megs of ram
When I had my old computer the software was unuseable, it was a core 2 duo 2.4 with 2gb ram
I am on quad core 2.93 w 12gb ram and it scores 7.3 on win7 x64 and it is perfectly useable..
I had some glitches but it is calming down now.