I'm the opposite of everyone here. Spotify is so good for discovery. My discover weekly consistently finds me awesome little bands I never would have found anywhere else. The mixes and playlist generation are terrible. The service is good. Offline mode is terrible.
I still send music I think is cool to my friends and vice versa. Being able to see what your friends are listening to is also great.
I'm still switching to my own music library using listenbrainz for discovery. Hopefully i can still find good music.