The problem with spotify is two fold.
First, the labels have them by the nuts which is what's caused it to go from free, with some adds supported by almost zero bandwidth because of users caching.
Second, it's essentially a sell out. It successfully provided an alternative to torrents that encompassed the sharing aspect, the problem here is there are plenty alternatives that don't have adds. Also, all of the additional devices "supported" are just thing which work out of the box with a cd/mp3 that isn't riddled with drm. At some point people are going to realise someone can just flip a switch and remove all their music.
My personal problem with spotify is their use of my bandwidth. Using p2p was a way to reduce their costs so they could run an add based service. What happened (and most people seem utterly oblivious) is the music industry bullying spotify into charging people for a service but continuing to use their bandwidth (not providing the user any controls) in order to boost their profits. It's like BitTorrent DNA. Did you know some of the uTorrent team were behind spotify yet there are zero bandwidth controls. Fine for most people, until you remember that most people have other people in the house who like to watch videos, play games and use voip without something creating random spikes.
The thing is, since firefox added app tabs I've had that little grooveshark icon at the top right of my browser for ages now. It's more convenient, doesn't bombard with adds and it easier to manage via qos. I'm happy to suffer adds (most of spotifys here were nhs ones in scotland, or related artists) and use my bandwidth to make it possible, but the majority of people who took part in the beta the other year did so because of it's p2p sharing aspect.
It worked, it reduced the number of people using torrents but the same people who created the torrenting problem originally have only be destroyed, thus pushing the very people they successfully removed from the problem, back to the problem. Have problem, create spotify solving problem, slowly bully solution until it replicates original problem but at a price point equal to high connection vpns....
Einstein defined insanity as doing the same thing again and again and expecting different results.