In respect of Spotify....
As a user, I have found it to be excellent. I have been amazed at the amount of ambient, electronic, prog rock and music for my tastes that are on there. I though it would be more for the younger generation and thus full of utter pish music
This is not the case.
I use it to stream on the higher quality setting which I believe is 256kbs , might be 320, and the quality is not too bad at all. Whether over the PC and cambridge PC speakers or through my ipod into the main hifi.
Whilst it would appear income from plays may be on the low side I have found myself buying several CDs and downloads as a result of researching on Spotify. So perhaps that should also be considered, ie a way to showcase ones music also generating sales. Off course there is no way to quantify that.
Personally I think Spotify is superb.