If you don’t really need a lot of options and looking for a simple Bittorrent client, then something like the BitStormlite or Gnome-bt might get you interested.
But for all you command-line lovers ;-), ‘CTorrent’ is also another command-line based features rich Bittorrent client that is worth checking out too. Now there are few others that you can try, but in my experience, ‘CTorrent’ is one of the most user friendliest.
Few main features …
*. Set download/upload rates (when launching the program or can also be changed on the fly).
*. You can set it up to automatically exit after reaching a certain share-ratio or after a several hours.
*. Change max peers/seeds per torrent.
*. Change port (useful if you have a router and have disabled “uPnP” which usually requires to forward a network port manually).
*. Change disk cache, update tracker list (useful for speeding up things a bit), automatic hash/integrity checking (resume from the last interrupt), manually change file save location, enable disable verbose outputs and more.

*. Supports running CTorrent as a daemon (runs from the background, even after the Terminal window is closed).
You can install CTorrent in Ubuntu 12.04 Precise Pangolin, 11.10 Oneiric Ocelot, 11.04 Natty Narwhal, 10.10 and 10.04 by using the below command in your Terminal window.
sudo apt-get install ctorrent
How to use it ?
Adding a Torrent file is extremely easy with CTorrent.
Let’s assume that my torrent file is called “precise-desktop-i386.iso.torrent” and it is saved in my “Home” folder. Then to start download it (without changing any settings), I’ll use something like the below command.
ctorrent Downloads/ubuntu-11.10-desktop-i386.iso.torrent
Replace your torrent file location and name accordingly (marked in Green).
A little about the “downloading status” section …
Now it might look a bit confusing to some at first as when looking at the below “status” section (marked in “Red”). I won’t go into all the details but only describe things like Download/upload speeds, downloaded amount total peers etc.
*. Just above the Status line, you’ll see the total file size of the downloading file (695 MB in this instance).
1. The first one marked in “Red” shows the total number of: seeders/leechers/and total users.
2. Before downloading BitTorrent protocol splits the file into small pieces and the second one marked in “Green” shows: Pieces that you’ve acquired/total pieces/pieces available from you.
3. The third one marked in “Yellow” shows: downloaded data/uploaded data (both in Megabytes).
4. The forth one marked in “Blue” shows current: download/upload speeds.
5. The Field next to that represents (marked in “White”) an average download/upload speeds, of the torrent file.
How to throttle download/upload speeds ?
CTorrent uses unlimited upload rates by default. And unlike with many other file sharing protocols, BitTorrent depends heavily on your upload slot to communicate and to share your torrent files with others. But if your upload bandwidth is too high then it can slow down the download speeds too. So the best solution is to find a balanced upload speed.
I cannot give you certain values because the optimal upload rate depends on your Internet connection (its bandwidth), nonetheless, changing the “unlimited” value is a must.
Let’s say that I wanted to download a file by using 100 KB/s (kilobytes per seconds) for download speeds and 10 KB/s for uploading, then I’ll use something like the below command.
ctorrent -D 100 -U 10 Downloads/ubuntu-11.10-desktop-i386.iso.torrent
Remember that the keys are case-sensitive. The above command uses capital “D” (for download rate) and “U” (for upload rates).

Changing the saved location of a file …
Let’s say that I wanted to save the file using a different name in a different folder (by default saves the files in your “Home” folder). Then I’d use something like the below one.
ctorrent -D 100 -U 10 -s /home/gayan/temp/new.iso Downloads/precise-desktop-i386.iso.torrent
The “-s” argument is the option that defines the file path and name (optional).
If you want to get a list of commands, then simply press the “h” key (while downloading a file) which should give an output similar to the below one.
How to exit it ?
You can press “Q” (capital) and when asked, confirm by pressing the “y” key.
Manually updating the trackers URL?
For that, you can use the “-u” argument. Again for the above torrent, I’ll use something like the below command.
ctorrent -t http://trackerurl Downloads/ubuntu-11.10-desktop-i386.iso.torrent
Replace, “http://trackerurl” with your tracker URL.
If you want to get additional information, then please read Ctorrents’s manual. Use the below command for that.
man ctorrent
You can also visit this official CTorrent home page for more. Good luck.