Well, Banjiman, I found myself buying a lot of CDs I've listened to once...or less often than that. I like Spotify very much for exploring music, but don't mind buying music that I'm going to listen to in the car and other locations. I suppose Spotify works well for performers who have tens of thousands of fans, but not for those who appeal to a limited audience.
But Spotify is an excellent place for historic recordings that I'm going to listen to only for research - and for most of them, the performers are long dead.
-Joe-