Ever since I switched to ubuntu I've noticed my chronic torrent-downloading habbit has decreased by leaps and bounds. I think this is in part because there is a lack of decent bittorrent clients on linux. I know there is azureus, but it consumes a lot of ram and I haven't had the best of experiences with it on ubuntu.
There's hope though, and it's not uTorrent, but it's close. It's a client called Transmission. It's small, fast and sleek. It works really good, and I get the same speeds I achieved with azureus on windows xp, so no problems there. Still, there seems to be a problem with Transmission and some tracker sites, like demonoid. This bug (I think is a bug) makes your ratio go up or go down, so it's risky, but this has been reported with the svn unstable version (0.7.x I think), so if you're having problems just downgrade to 0.6.1 and you're good to go.
If you're searching for a nice bittorrent client on ubuntu just do sudo apt-get install transmission-0.6.1 and try it out!