"Ok, now put the play bar on the left. No wait, the right. A little more. Good, right there."

Users would put up with this for about 10 seconds before just grabbing the mouse and dragging things where they want them.

I think that's why voice interfaces have not become popular. PC applications tend to be developed for a direct manipulation (window, icon, menu, pointing device) paradigm, so adding a voice interface doesn't help much. A useful voice interface requires an entirely new UI paradigm.