i think it's great. I don't really listen to music unless i want to check out a particular band, but it's great if you want to see a bands history. Or even if, for example, someone says "did you realise that Pinball Wizard starts with a Baroque riff......".
In effect it gives you immediate access to just about any music ever made... although that leads to the biggest downside, and that is that many bands choose not to allow their music on there..... for example Zeppelin!