Decided to give Google Play Music All Access a try. I've only been using it for less than half a day, but it's pretty great so far! The radio feature is not that much different than Songza (you can select a station based on your mood) or Rdio (you can select a genre or artist-based playlist), but I haven't even dived into the ability to stream any song/album in their database.
Either way, I'm quite impressed! At $10/month this is almost the perfect music service for me - the perfect service being a flat monthly-fee with free downloads of unlimited number of songs. $10/month for streaming is pretty close.