I agree on the need for the arbitrary canvas rotation usable with keyboard+mouse/pen input. When I work, my left hand is set on the keyboard and right hand draws on the wacom. While I can somewhat do it on the macbook the left hand hand to magic pad and rotating fingers there, it is clumsy and unprecise in practice. My compromise has been to create keybindings to have rotate left and rotate right buttons on keyboard, but you'll have to slam them multiple times to get where you want. That workflow is slower than it should be, as when I'm painting, I'm constantly rotating to the canvas to align optimally towards my pen. I would love to have it improved as proper tool, so that you just press the key once and use the mouse left/pen to define rotation angle on the go, similarly as it is with the magic pad. That will improve the desktop painting workflow significantly.