The site does bad job explaining itself, and therefore only makes sense if you already use last.fm. The UI is crude (javascript links with 'href="#"' which bounce you up to the top of the page all the time, etc) and inconsistent (nav bars come and go).

I think it's an awesome idea, but I think it needs some TLC from a good web developer. (And to be fair, here, I don't claim that I could do any better -- I'm bad at web UIs, and lean heavily on others when I have to make them.)