I like Spotify's discovery. I subscribe to a lot of playlists that are constantly updated where I can get a lot of new artists from. Never used the radio, I just go to their playlists and find Americana or Alternative or whatever I'm looking for.
I know it sounds like whining, but I really think the 'killer app' of music will be something that can effortlessly pick out the unknown gems from the ocean of new music. I'm continually surprised about the quality of new music but I don't like to have to dig around for it my self.
Though, I wish there were better ways to discover people to follow, it's fairly manual now and much of it goes on outside of Spotify.
Spotify playlists are beautiful because you subscribe to it. The playlists are updated and curated continuously. This is true of the Spotify-published playlists and those of musicians, celebrities, etc.
Spotify boasts a gigantic library, I cant imagine I've heard everything good (objectively) already. There has to be thousands of hours of material that I simply can't find that I'd otherwise love to hear.