I've just got on to this, it's superb! Been recommending it to everyone I know. The hours you could spend on this is frightening.
I known that it doesn't have every song or every band but it still has bleedin masses of songs. Only just realised the 'import playlists' function from the above websites. What can I say, if you can find a way of using this whilst mobile it does away with the need for mp3 players. There's the future right in front of you. Never a need to 'buy' music ever again, though I have to admit that I've been trying before I buy on Spotify for a couple oif bands I was dubious about buying their albums.
Blimmin great stuff!