To my own surprise I've lately found myself listening to a LOT of music on Spotify.
I opted for the premium subscription giving me higher resolution *cough* whatever *cough* streaming and it's really wonderful being able to listen to whole albums you just heard someone mention (here on gs for example) in decent quality.
Then if I like what I hear I order the CD, especially for albums where the sound intrigues me more than the music (even better if both is the case).
Previously I did the same kinda thing using iTunes buying the music there then buying the CD if I wanted the best possible quality but Spotify saves me quite a few bucks and the instant play is really really great. Also good to have in the studio if you have a client go "make it sound like xyz" ...