I'm pleased with the release of Google Music, as it allows me to store my entire 15k+ tracks for free on google's servers, the same thing Subsonic lets you do running your own pc as a server. The Google Music Android app is not bad, it's good looking, though maybe Subsonic Android app is a little easier to navigate where you want to go. But problem is, when you use Voice Commands (Voice Search) on your Android to play your music, the Google Music app will not play unless you specify an exact song title.
If you voice command Subsonic to play an artist, it will select a track of that artist and start playing - Very good when driving. Do the same with the Google Music as your default music app and it will stop at that artist, throw up some possibilities and a keyboard, which ruins the value of having voice command, you are back to fumbling with layers of touchscreens instead of watching the road.
Google Music is great in that the storage is massive and free, and if your Subsonic home server stops working while you're away, you can open Google Music app to get at your collection. Thanks Google. But Subsonic is still superior for remote Android listening and voice commands.