[sping]

It's mostly the TrackPoint for me, and I've worked with quite a few trackball users.

[rgoulter]

You can distinguish a trackpad from a mouse, in that stuff like "multi-finger gestures" or "pinch in/out" makes sense on a trackpad but not a mouse.

Whereas, a trackball is roughly the same as a mouse. (Albeit, much more comfortable to use, IMO).