Deluge
I have been using Deluge on my Ubuntu 12.04 server for ~7 months now and it is fabulous. Allows me to do everything I have hoped and more. One feature I would like to see is a one click button some ware on the main screen to allow me to throttle all torrents when I am streaming, gaming, or whatever is needing more bandwidth. It would have to be adjustable too. I am aware I can open preferences and throttle, I just think this could be improved. Perhaps have the ability to have a timer/alarm feature along side this for when you forget you throttled.
Satisfied Deluge user.
JDDonks