Pros: - I've tried lots of trackballs and a few vertical mice, and this is by far the the best ergonomic design. Satisfying click, does what you'd expect a mouse to do in every other regard. - Also was delighted that it has an on/off switch AND a holder slot for its dongle. Totally comparable to Logitech in this regard. - Never had any software malfunctions, always starts up quickly on any computer I plug it into.

Cons: - As mentioned in other reviews, the back/forward buttons are kind of in the way, and not particularly well placed for ease of use. Not a big deal. - Relatively cheap materials. After only a couple routine accidental drops, the scroll wheel broke. This is because the tiny plastic rod that turns the scroll sensor is REALLY TINY and therefore brittle. I managed to fix it with a ground off piece of an equally small Allen wrench/hex key. But taking it apart was nearly more trouble than it was worth. You have to tear off all the foot pads, and palm pad, therefore reducing the quality of the glue holding them on. Nevertheless, they've continued to hold after taking it apart twice now.

Overall Review: Overall an excellent buy. Above and beyond for the price, especially in comparison to competing brands of similar design. Great for hand pain relief (I recommend turning your cursor sensitivity DOWN as well to reduce movement of the hand/wrist, and use your whole arm more), great mouse regardless. Can't go wrong for the price.