BitTyrant is a fork of Azureus that has an average of 70% greater download times than Azureus. BitTyrant's codebase is simply Azureus 2.5's codebase but it was modified. Plus BitTyrant's GUI is the same as Azureus, so I see no reason of not replacing Azureus with BitTyrant.
Link: http://bittyrant.cs.washington.edu/
