It's difficult to control the slider-dot in the time progress bar during playback.  One's finger obscures the blue dot one is trying to move, requiring multiple touches to try to get it to be where you want it to be.  Perhaps the dot could grow in size when touched, and thus allow dragging, with the times at the ends of the bar changing as the dot moves?

Also, the volume control cannot be moved by touching along its track, but only by dragging it.  It would be nice to be able to touch the righthand (high-volume) end of the track when the slider is at the lefthand (low-volume) end rather than dragging the slider up.