Does anyone find rotation controls such as the one in the linked site usable?
Do you mean unusable?
I find the sensitivity way too low. By the time my mouse is off screen, I should have rotated the thing more than 60 degrees.
I mean usable. When I rotate something I want it to rotate in logical fashion and be able to get back to a point that I previously saw. Rotations as implemented in this site seem willy nilly and I can't think of any actual case in which I'd prefer this behavior over a local yaw to a global pitch.