For downloading large file, edonkey do a very good job of utilizing all bandwidth avaliable by chaining people who download the same file. If you are downloading a file, it will automatically fill all upload slot with people downloading the same file even you haven't fully obtain the file. This lower bandwidth load on the person that has the original file. Everyone also has about the same ul/dl ratio which is very nice. It doesn't matter whether you are 56kers or T1er. They all share the same ul/dl ratio. Also, the problem of leeches automatically goes away.

For developers, just use edonkey to download a hard to get large file and you will see how it works..:P