Tor is specifically designed to make it hard to torify bittorrent. The tor developers state quite clearly that tor is not designed to handle the kinds of bandwidth required for p2p file sharing.
I've used tor in the past. And I know where they're coming from. Loading a web page through tor can take upwards of 30 seconds sometimes. Compared to 1-2 seconds normally.
The only semi-sane way to run torrents through tor is to only torify communication with the torrent tracker. All actual bulk uploading / downloading should go direct, not through tor.
edit: cyberjock beat me to it.