[dbond]

Looks good, nice to see spotify integration in an app. Though I'm curious as to how you're getting around section 3.3 of the libspotify (assuming its use) terms of use, or if you didn't know about that then I'm here to throw a warning at you...

  3.3 You may not sell the Application, charge Users for 
  use of the Application or otherwise derive any income 
  from Users’ use of the Application, such as through e-commerce 
  initiated via the Application or the sale of any advertising, 
  sponsorships or promotions on the Application itself.

Not trying to be that guy, but having your spotify streaming access revoked could leave you with some angry customers :)

There are also some smaller clauses in there that may restrict the streaming from multiple providers. These terms don't seem to be based on any kind of logical reason though.

[waxenfigurine]

Perhaps the author can come to an agreement with Spotify to integrate their service under different licensing terms. It might run into money, but that can be cast positively as forcing more clarity for the revenue model.

[morrisirrom]

It requires Premium spotify membership to make use of those features.

[dbond]

If you haven't spoken to spotify about this you might want to double check that, any usage of libspotify requires premium, these terms still apply.