Be careful with tune up utilities, if you select an option without knowing what it does you could potentially damage the operating system and have to perform a reinstallation. It doesn't happen a lot, but I've seen a few utilities out there that manage to mangle things pretty badly.
Mac OS X tends to clean itself up pretty well as far as removing old temporary files and caches, and the file system that it uses isn't as prone to fragmentation like what you'd find on a Windows-based PC. In my opinion, there's no real need to fiddle around with un-necessary tune-up software.
Just my two cents.