Recently came across metalink. Sounds real promising. This would probably be what Shareaza should be. Running BT, G2, G1, HTTP & ed2k all at the same time sounds real painful (and it's a big headache for the developers too).
A single .metalink file that allows the client to connect to multiple servers/trackers simultaneously to download a file makes life simpler, I think. With metalink, if a server is down the download manager simply continues to download from the other sources provided in the metalink.
Now, if only I had something I want to download that's available in metalink. Maybe Ubuntu will provide metalinks in future. Many Linux distros and *BSDs are already available through metalink now.