I too was wondering this. Having had my Mac Pro for a while now. It does seem a little sluggish these days. Photoshop and the such are not running like they did.
I know on my windows box I used to run a program called atf cleaner. I have plenty of disk space etc.
Anything you guys can recommend? On a side note I have close to 400 fonts installed on my main machine. Was wondering if that could possible be an issue but 400 does not seem a like a lot to me. Could be wrong.