+++: The "Scroll ring" is great! To my big fingers is much better than the classic wheel! (One can only regret that it is too "soft" and there are so many game: it's a little "cheap", but at this price point ...)
+: Large buttons
+: Stability and low profile (normal for a trackball!)
+: Beautiful object
0: Symmetrical therefore works equally well for left and right-handers
-: As the ball is big middle fingers are raised enough compared to the back of the hand, resulting in tensions ... however, it is not obliged to keep it that way and vary the positions relieves the hand
-: No "middle button" followers of Linux consoles, hold you to say! (Well, with a little practice the left-right simultaneous support is very good)
---: The "push-pull" are a pain: we must keep the support of the thumb and little finger while maneuvering the ball with others!
In short, it was not a miracle solution for me, and I recommend the "gamers". By cons, she replaces my mouse to work :)
Namely: the box contains additional support which offers better extension of the trackball to avoid "breaking" at the wrist (extension of the forearm) additional length: about 5cm