I gave up my $7.99 "early subscriber" with Google+ to go back to Spotify Free. After I wound up not being able to listen to 1.) Sigur Ros 2.) Boards of Canada and 3.) Scale the Summit on release week (since G+ apparently didn't have them) and thus spending roughly $37.99 on music that month, I decided that paid subscriptions weren't for me.
IMO, though, Spotify is better on the desktop than Google+, just for little reasons. Last I checked, Google+ did not integrate with my keyboard volume and track controls. Spotify does. Just little things like that made me decide I'd go Spotify if I ever wanted to subscribe to something again.