On my iPad, using the iOS app, the volume control is difficult to use. Directly tapping the outer ring moves the control quickly. Tapping inside the ring (the inner circle) causes the volume level to jump very quickly, sometimes to dangerous levels. With a Max Volume setting in Playback Options, the controls will go past the maximum value.
edit: I was referring ot the iPad version of the app which is listed as being developed by Michaelangelo. There are two in the App store. Original report still applies.