Actually, there are ways to accomplish this. No stock way that I'm aware of. But, if you have WidgetLocker for example, you can add the music player to your lockscreen. This has helped out tremendously while driving.
The only bad thing I can say concerning Google Music is that early on it deleted about an album and a half randomly from my uploaded files. Just wasn't there one day. Besides that problem, everything has been smooth as silk. I especially love how your last few albums listened to stay active so that you don't have to wait the few seconds for a song to load when switching to another artist.
what i like to do is pick the songs i like to listen and make them available offline so i don't have to deal with the loading