+?? where are we? -- For uTorrent. You'll probably need to get uTorrent 1.6, though (previous build), as many torrent trackers are not allowing the most recent version (1.7).
I really liked Azureus, which is what I used to use, but it was a little batty in that it wouldn't let me limit my ul/dl rates. I mean, it'd let me, it just wouldn't do it. uTorrent has proven to be very stable, so I've stuck with it. As far as features go, I really preferred Azureus, but that one minor bug switched me over to uTorrent. After a year or so of using uTorrent, I've gotten to like it. It's really easy to use and the scheduler is just so simple to use and so well done. I wish there was a search feature, though, like to search for a particular torrent in my list of torrents, using a keyword (it can be hard to find stuff, sometimes!).