The issues I refer to are the following:
When listening to an album or instant/random mix, it'll play the first three tracks before the application becomes unresponsive. The menu, back, pause/play, track forward functions - all functions really, become unresponsive. I have to force stop the app before it works again.
On occasion when listening to those first couple tracks, the first track plays normally through my AUX jack (ie, plugged into the car), the second track will for whatever reason, play through the phone speaker. I have to disconnect the cable and plug it back in for it to work normally. Of course the music stops (which is fine...i understand why it would stop on changing of output options), and I have to restart it...AND of course all the volume settings (because Samsung is stupid with how it handles volume settings). It's fairly unsafe in the car fiddling with all this stuff, just for a basic use of such a device in the car environment.
If you look at the Google Music app comments for folks with the Samsung, they're having similar issues. I've opened a ticket with Google on it, providing feedback. I've also removed the new music app and the old stock JB version of Google Music (4.3.something) works normally.