Dunno if this will work for anybody else, but if youve noticed your version of osx getting sluggish as time goes by (Im on mountain lion), reindexing my drive gave me a huge speed boost. There must be a bug somewhere. Initially spotlight wasnt indexing right (unrelated to the slower and slower program access times... Ive an i5 and felt slower than my core2duo) so I went to reindex which took 10 secs (a couple hours to actually reindex the drive), and got this completely unrelated massive speedboost. Back to what it was originally when I got the computer.
As usual, with all things computers, it might just be my particular situation and one of those 'odd things'. But figured maybe someone else will benefit.