It's a streaming app. 15 million songs. I got an invite about an hour after going to the Amanda Spotify place. Just Google search for Amanda Spotify invites. I think the program has been in Europe for years and I guess they could never make a deal with all the music publishers here.
They have all of Robin Trower's catalog and even Robert Mirabal is fairly well represented so that what is so cool about it is that they have some music that a lot of folks never heard of.
I think the cost is going to be around eight bucks a month for HD music streaming to your phone if you like that sort of thing. I'm running Audiogalaxy on my home computer which serves/streams up my music collection to my Droid X full time anyway so I probably won't pay for the full Spotify service. I expect it will be very popular though with the 15,000,000 songs they have. I expect people will pay a small sum of money to be able to play any song or playlist, at any time, anywhere. That is the trick I guess, keeping it cheap while keeping the music industry happy, or at least at bay.
I also have a 120Gb Zune that has all my music on it anyway. Add some nice Bose headphones my lovely wife go me for Father's Day, and I am good.