KTorrent is a full-featured, graphical BitTorrent client for KDE. It has a rich interface as well as support for magnet links, plugins, stopping/pausing and resuming downloads, extended torrent and peers information, system tray integration, plenty of configuration options.
Transmission (bittorrent client) 2.10 was released a few days ago, and while it doesn't bring major changes, the new version includes several performance improvements
In this article, I will cover installing and configuring transmission-daemon in a headless (but should work on a normal Debian / Ubuntu install too) Debian or Ubuntu machine. You can then use Transmission Remote GUI to control transmission-daemon, remotely.