GameBall Daumen

Basic trackball functionality is the best I've ever used. High sampling rate, high accuracy, low jitter. Every other trackball I've ever used, even though they get other elements better, would be 2 stars in comparison. The insanely low [and jittery when scaling is up] tracking of Logitechs is just unbearable in comparison.
More buttons [ring & pinky, and a couple around the thumb trackball] and side-to-side on the wheel would be very useful for a lot of tasks.
Adjusting settings is clunky, ways to configure/script settings from the PC would be an enormous improvement, particularly if open so it can be done cross-platform.
Accidentally hitting the speed switch near the ball and switching speed is incredibly annoying, having to cycle through settings to reconfigure it while playing is painful.
LED feedback is always green while in use, would be much better to have connection/charge LED separate from speed indicator.
Only useful setting I've found for the LED ring is off. Again, an API would be useful.

Mixed feelings about the shape of the palm rest & bumps under the palm, which hit the wrong place for my hand and are a bit uncomfortable, but they also let me know where my hand is on it, which is useful.

This Trackball mouse works better then any I have used before like ones from microsoft or logitech they have issues with their buttons going bad the switch part also their trackball is not as accurate or fast as the gameball the only weird thing is Linux mint just released a new kernal & when it installed the gameball mouse was to sensitive I had to mouse settings down in the mouse settings to its lowest level not gameballs issue but linux kernal update

GameBall Thumb

I bought it to play Counter Strike with other friends of mine who use trackball mice. It’s fun.

The mouse is great, I find it very comfortable. I did have to return the first one since the ball movement didn't feel right for me. However, Eric offered to personally test the replacement one before sending it to me to ensure that it had no issues. The replacement one I got is perfect. I'm definitely going to snag the Gameball Pro when that releases. Thanks Eric!