Like many I am very happy with the product. Visible tests on the net will point the finger too heavy a burden and not top performance. This is can be true for gamers and other heavy users. Personally, I use it at work, and it's great. I was afraid of the size and weight, finally she is not bigger than my other Logitech mouse is comfortable and weight (160 grams without the wire). Additionally the super skids allow it to move easily. Nickel Response time at my level. The recess for the thumb is great. 2 complaints: the Next / Previous buttons are too high for my taste and demand a greater joint of the thumb as my previous mouse, damage to this mouse so almost ergonomically perfect. Then in the same idea, the roulette release button for large scrolling is not easily operable and also requires a gymnastics index.
