The first ones I tried ( this is about 9 months ago) where Gnotella and Bearshare, but beeing a napster (gnomeplus) refugee I was dissapointed by the succes rate of the actual downloads.
Then I decided to try Phex 020, it gave not so much search results as the other 2, but when you clicked on one most of the time the download would actually start.
Back then Konrad H was developing phex and you got a improved version almost every week
So since that time I have been using Phex.
I have also been trying Limewire, Gnucleus and Xolox, and alltough it has a buggy Gui at the moment, Phex is still my favourite, it just does the job the best