I checked out the Gamespot stream and Danny O Dwyer says he played with Keyboard and Mouse during his special preview and said that "keyboard and mouse seems to fits a bit better." Then after a little more time with the controller he says "its way harder to control with a controller, yowzer". Take from that what you will.
Well, IIRC Danny is a seasoned PC gamer himself so I suppose he's used to mouse/keyboard controls. It's good to hear that he actually prefers M/T in Witcher 3 but it doesn't solve the problem that the game is most likely quite unoptimized for that kind of input, especially the UI elements.
And after all, sometimes it's hard to seperate "controls" from "gameplay/design". Sometimes the implementation of controls are bad, sometimes it's already the underlying design that's bad. You can't really know that without a serious assessment.