install sp1 it gets much better. I didnt use any tweaking software but
if you are not using windows' search thingy stop windows' indexing, auto defrag and some other features like that, it saves you some ram/proc. (well tehre is and option like "do it only in idle", but it starts to it in games etc. it slows down.)
And i run ccleaner everyday. It's like 1.5 months past from fresh vista setup, it still runs like in it's first day.