Quality-wise, this is great. So far everything works well, and I haven't had any problems. The features are solid, and the buttons work. But, the vertical mouse isn't for everyone. I apprehended one because everyone says they're more comfortable. They are not.
I was quite happy with normal mice but I heard so much about these I had to give one a go. My styloid process is jammed on my table and I have to press in on the mouse with my thumb and fingers to push buttons.
There's also no quick movements from the keyboard to the mouse anymore since you have to grip it instead of just shove your hand onto it, and it's tall so half the time I smack it right off my desk.
However, those are ergonomic mouse gripes common with all of them.
If you know you want an ergonomic mouse, this is good! If you aren't sure, and your mouse doesn't hurt your wrist, then you don't need one.