Some people have reported problems with it, like corrupted files, but I've never had a problem with it. This way, I can get a file, and seed it all night without killing my whole connection, some of which is needed for um, other things...
It also works great for people who have a hard cap on their cable modem. I got faster downloads (all 30k of bandwidth

http://a.wirebrain.de/torrent/clients/
That leads to a download page for the cappable client. Don't be a dick, share a reasonable portion of your upstream.