Tixati is a free, simple, and easy to use P2P client that is compatible with the BitTorrent protocol and also supports magnet links. I probably wouldn't have read about it if it didn't work on Linux, but that made me take a closer look and so I got to enjoy Tixati.

Tixati works on both Windows and Linux and it has a somewhat different user interface that what you are probably used too, which you can change: treeview, tabview or split and also dark or light colors, as you can see in the screenshots below: