Actually, my favorite BitTorrent client is BTQueue but the latest version has some memory leak problems for long run which I have no idea how to solve. My plan is to replace its backend to something native because Python memory management is not suitable for long run and heavy memory consumption applications like BitTorrent client. My current backend is rtorrent written by rakshasa on top of libtorrent. Anyway, I unified rtorrent to make it run separately behind BTQueue and let BTQueue talk to rtorrent via XML-RPC. Unfortunately, the new BTQueue is not usable yet so I have to let web-based client to call XML-RPC directly to rtorrent.
I just got some good idea from my friend, romerun. He suggested the idea to combine social network and BitTorrent together. As of now, most trackers offer a search page to find or browse the most recent torrent files. Once you look at each user detail, you will see what torrent files you are seeding or leeching. Anyway, it would be better to apply some social concept to bittorrent trackers.