Using here the REAL champ: Azureus... best BT client by far, although a bit on the hungry side, resources-wise (natural- it's a java based client).
Under settings/transfer, I've set max.simultaneous downloads to 5, connections per torrent 15, max.uploads per torrent 4, max.upload speed 11. Using more simul downloads results to crawling, using more upload connections virtually bans me from browsing... Connections per toreent is a slightly more flexible setting, my "15" is rather empirical.
That is for my "slow" 384/128 ADSL connection, you can adjust yours according to your D/U speed.
In 95% of the cases my BT download speed is 3-4 times faster than any "Mule variation"... I am using MLDonkey, which is surely buggy (although not less than the majority of Mule variations) just because a. It can run as a service, using zero CPU cycles and 5-6MB of RAM, b. is multiprotocol, bittorrent included (but the implementation is still very crappy, eg the uploads are killed once you finish downloading, so some torrent sites have blacklisted it... plus more annoyances), c. Not really faster than Donkey/Overnet, maybe a tad slower, but the search option returns much more results, d. It can be controlled remotely AND completely via Browser or Telnet with or without SSL (putty). In fact, it's best GUI is the embedded browser one.
Not a bad set of options for a P2P client, isn't it?