Out of curiosity (as you both clealy use these trackballs), what's the selling point of them, what's attractive about what they do?

You'd have to try one to understand. It's not hand motion, it's only finger motion.  I don't have good control when moving my arm, but all I have to move is a finger, usually two on the ball, thumb on left click, pinky for right.  Never runs off the mousepad, no need for one.  Sits right on the keyboard drawer, no problems.  I don't even have to look anymore, just move my hand and it's on the ball. Doric.

The "I" in Doric is Silent.