Just wanted to let you know that in the next update (being submitted in the next day or so) all settings, including shuffle mode, will be available for changing in the app itself rather than in the Settings app. Shuffle mode will also be changeable via a new gesture on the touchscreen, so we hope this will make thing simpler.

We don't allow the screen to lock, since that disables all touch input and would force you to unlock the phone to regain control, which may not be safe when you're driving for instance. You can still lock the phone manually of course.