Seeing that this was the Amazon equivalent to the Logitec Performance MX full-size mouse (at half the price), I decided to give it a shot. First thing I noticed upon taking it out of the package was that the pad at the front end of the mouse was not as thick as the pad at the back end. Any time I clicked the buttons the mouse would rock on the uneven pads. Easy enough to fix by adding a few layers of scotch tape over the front pad to thicken it up, but disappointing nonetheless.
Once that was fixed, I started using it. It's definitely ergonomic and comfortable to hold. It's also pretty smooth on larger motions, though it struggles a bit with small movements. I doubt it would be enough to bother the average user, but as someone who uses this mouse a lot for computer drafting (which requires small, precise movements) it can make things more difficult than they need to be. At least the extra buttons are well placed. If you're not the type to use them, you usually won't accidentally hit them. If you are the type to use them, they're close enough that you won't need to contort your hand to reach, and they feel pretty solid.
I've also noticed that this mouse burns through batteries like nobody's business. It's now on its 3rd set of batteries in 5 months. At 2 batteries a pop, that's pretty bad. For reference, I treat this mouse pretty similar to the way I treat my Logitech M510 mouse and the M510 usually goes a year-plus without needing new batteries.
Overall, the bells and whistles are well-designed but some of the basic functionality feels like it's been overlooked. It's a good deal for the price, but if you need a performance mouse this isn't quite it.