In summary, using Tor only hides your IP address from the tracker. As has already been mentioned this will mean you will only be able to receive incoming connections through DHT, Peer exchange and local peer discovery. The Tor network forbids P2P data traffic. The only anonymising system that actively encourages P2P traffic is I2P (http://www.i2p2.de/), however uTorrent does not currently support I2P. Also, using I2P for torrents is very slow. (The only client that I have found reliably works for I2P torrents is the built in client I2PSnark). The painfully slow speed of torrent downloading is in part due to the very small number of peers using I2P for torrents, but also due to the overheads the encryption and anonymisation process involves... Anyway, TOR does not provide the sort of anonymisation that people are looking for - so you have to ask yourself, why bother ?
