For connecting to private OpenNAP servers, this is simply the best Mac software. In some ways, I even prefer it over the popular WinMX on Windows.
I think people rate this software low because they do not understand how to use it. If you're trying to do normal P2P where you connect to a mass peer network, it sucks. If you have access to a private server with files based around what you are interested in, it is very fast and reliabe.
I have downloaded 60GB+ of music video files using this software, it's very useful.