I normally use the built in torrent engine for Opera, though, I always consider torrents as a last resort option. Direct Downloads are much more efficient, unless you're downloading something thats like 80GB or something :laugh: .
Actually it depends on your connection, in my case, Direct downloads are the least efficient means of downloading.
On topic wise, I use utorrent, of the ones I have used, it works best if you are confined to wireless internet. The others don't pick up when the connection is low.