I like Deluge, although Transmission is the torrent client of choice for Ubuntu.
Deluge does all that I want it to. Azureus has lots of features, but it is a bit
of a resource hog. I am not sure what other torrent clients people are using in
Linux aside from the usuals, bitTornado and bitTorrent. There is a tend toward
more inclusive clients which serve double or triple duty such as handle file
sharing (a la Shareaza or Frostwire) or file downloaders (such as Aria2).