I agree that while driving in a car it might be tough to push and twist... Hmm.

Then how about the idea I asked the Empeg guys to implement... A single knob push toggles it between two different states. In one state, it controls volume, in the other, maybe it seeks within the song, or jogs between songs... In fact you could make it three states... There'd have to be some visual feedback as to which you're in, maybe a tiny icon in the bottom right or something. And maybe some audio beeps... Hm.


edit: It wasn't until after I posted this that I realized how funny that "push and twist" comment sounds... Somewhere, Beavis and Butthead are laughing hysterically.