I found the knobs took a little while to get used to.  Mainly when turning the knob down.  I would put my finger on the knob and move it downward and run out of screen space.  However, I found that I could put my finger on the knob and move it too the left and have loads of room to turn it down.  I like the fact that there is not any faders, a knob takes up a lot less room on the screen than a fader does.  If it had faders, you would have to scroll to another screen to see all the faders.