One problem I've had with Sketchbook is that - even with pen mode enabled - I managed to keep on selecting the wrong layer or some other control simply by the way my hand rests on the screen.
I realise palm rejection & pen mode relate to unwanted brush strokes, but perhaps this could be extended to include the controls so that non-pen touches are excluded from any click or selection? (or maybe add an additional option to the preferences to allow users to choose to work this way)
I see that you have the option to hide the controls via a button on the top right of the screen, but this isn't really enough especially when you want to be able to switch from one control/option/layer/whatever else quite frequently.
