That's the one. And I also am grandfathered into the introductory price at $7.99/mo.
It's different from iTunes Radio--better comparison is Rdio or Spotify in that you can do more than just listen to radio stations. On Google Play Music, I can listen to any specific song/album in their entire catalog whenever I choose. I can build specific playlists or add entire albums to my library. Even better is I have uploaded my entire iTunes library into Google Play Music so I have access to it anywhere.
The app isn't the best as far as design goes but since they integrated Songsa into their service, music discover has gotten much better, IMO.