Spotify will officially launch in the US tomorrow morning

When I first heard of Spotify I was super excited (but it was quickly followed by disappointment when I learned that it wasn't in the U.S. yet). It did lead me to subscribing to Rhapsody which I have been pretty happy with. For those who have used both what does Spotify offer over Rhapsody (better UX, breadth of selection, etc.)?

I don't think they will hit their 50M in the next 12 months.

Most of the 18-25 yr olds I know use GroveShark at home or are happy with Pandora while on the move (if they are not listening to music they have downloaded.)

I just don't see the value added over other existing services.