i dont really torrent at all tbh but when i did for the odd demo etc i used bitlord which was fine, not an expert in this field though, just a friendly bump
Azureus is the best one I have used. Pretty easy to use, loads of control over torrents, loads of features, free and open source! What more can you ask for!
Bit Tornado for me
Has never let me down when it comes to downloading Linux distrobutions, gettin like 230kB/s (likes to choke my 2Mbps pipe)
Also has other features that let you specify maximum upload, maximum connections (which original Bit Torrent doesn't have), "Break seed bitfield" or sommin, to apparently foil ISP manipulation(yes, thats what it says), UPnP(so I don't have to thumb around in my router to forward ports, it is done automatically, and the Light.
Green means working fine. Yellow means firewall or portforwarding issue. Red means no connections at all. Blue means not seeing a complete distribution out there. Black having trouble connecting to tracker.
Possible this thread is an excuse to bash other people for using their clients, like with linux "SUSE is for noobs. Gentoo is a 'REAL' distro" etc. I hope not.
It is a little difficult to try out other ones, as you can only have on BT client installed at a time.