I know transmission works, but takes quite a bit when closing down. uTorrent works as well. I've been using both. One thing I like from transmission is that it shows the bandwidth usage on the dock icon, but I like the uTorrent UI better.
Transmission has a *well* documented bug that plagues a certain group of people it seems. Transmission will hang, beach ball, start working, then hang again, and repeat. Not sure what it is, but many people acknowledge that this happens, and it even happened to me constantly on my 15" MacBook Pro and MacBook Air. Fresh OS reinstalls, etc. Nothing could make transmission not choke.
But having said that, transmission is still great *if* it runs well on your system. Azureus is in second, and to me uTorrent comes in 3rd.
Lastly there is always the Opera browser that has torrenting built in.
Edit: I see a lot of votes for uTorrent, did they finally add the ability to select which files in the torrent you want to download? In the betas I tried this functionality was not in place, and it forced me to download every file even if I only wanted a few files from the torrent.
I'm running into some trickiness with torrenting in general on my system.
It happened all of a sudden, but I can't seem to run any of the major clients without my entire machine freezing up.
Transmission & Azurus both do it after several minutes of running, and uTorrent causes it if my machine sits too long. As long as I'm actively doing something uTorrent doesn't crash, but if it sits too long it does. As an example, if I leave any of these clients running overnight or while I'm in class, I wake up to a machine that has completely frozen, requiring a restart.
Mind you I'm not getting KPs, just...a standstill.
I'm running 10.5.8 on an EFIX based machine. Also, I don't believe the non-macness of my machine is to blame. I've been running it for almost a year strong and never had this problem.