It seems while Spotify was using its energy to defend its service for free business model while gaining entry to the U.S., the folks at MOG were in important ways building a superior only by subscription product.
Chris Connaker of Computer Audiophile in his extensive comparison of the two services notes two differences of import to me. First, though Spotify claims to have a larger library, MOG seems to do better in finding the stuff we want. Want the Dylan library? Pink Floyd? Big Star Live? MOG's got it, Spotify doesn't. (Neither have the Beatles). There are surprising gaps in Spotify, and some amazing finds in MOG. Want Phil Och's Canada-only release of Live at Carnegie Hall. MOG's got it. Go figure. Secondly, everything on MOG can stream at 320kps, i.e. near CD quality. Spotify is making progress, but, well, still working on it. Spotify has a glitzier interface, MOG works well enough even if it doesn't look as good.
But...there had to be a but...MOG is currently U.S. only and they mean it. Unlike Spotify you can't sign up and take your subscription with you. What about using a U.S. proxy server? Dunno, perhaps those of you now outside the U.S. will want to give that a try.
MOG is not perfect by any means but the seemingly more relevant library makes all the difference in the world to me and it's what I'm playing with in California. I'd say give it a try (at mog.com )and see what you think.
The Computer Audiophile comparison pieces are at: