Been using a thumb trackball for a few months, it's definitely better than a trackpad for long periods of use. I've tried rebinding the mouse buttons so I could play most light games without touching the keyboard, fun but impractical as mine would need a few more buttons for that.

Tracking quality doesn't depend on the desk surface, though is noticeably smoother after occasional ball cleanings. Overall an interesting experience, and at least better than gaming with wrist/forearm pain.