One of Spotify's gravest crimes is removing albums from time to time. I created a number of playlists, which now have greyed-out songs in them. I also don't see why they can't provide lossless audio. Having lower audio quality than the CD provided in the 1980's seems a bit of a shame.
But, having said that, I do use it a lot for finding new music. It's very good at generating recommendations and "radio stations" that cater to my tastes. This creates stress, though, as I then end up with a huge wishlist of music to add to my proper music collection.