Spotify is quite possibly best music service in existence. For me as a user it has saved me between $30 and sometimes $100 a month simply because I'm not buying music. There is so much that spottily offers, but for me most of all has been the cost in comparison to buying music from iTunes or Amazon.
From time to time, even though having an 8000+ music playlist, I still buy music because sometimes you just want to hear new music, and my collection has been listened to plenty of times, and new music is coming out everyday.
The reflex to buy music is still there. In fact when ever I ear music I like, I catch myself going for iTunes or Amazon music and then it hits me, -wait a minute, I have Spotify” I don't have to pay for it. A sense of relief comes over me, cause I just saved $10 or $15 dollar that I probably shouldn't spend. Impulse buy, averted.
From my general experience, usage, and interest in music. Spotify is a must have service. By paying what's roughly $10/month, you have access to the largest selection of music ever. Listen to new releases on a whim, or browse and discover new music of interest.
My only fear is that with a service this good, its competitors i.e: iTunes, Amazon working to shut this down. The loss of revenue must be noticeable