What is a geature?
Well, you have the + and - button at top of the device at all times. You can use those to control the volume at all times. Also, press dpad middle button to pause, which is IMHO enough the same as mute that I can't immediately justify adding a mute button. I really wouldn't like to fill the user interface with too much of stuff. Keep it simple, you know.

I'll definately focus more on the now playing screen for the next release. It will definately have a bigger cover image of the album as well as more information on the album (and multiple lines if needed).