Update 2 years later: I also have problems with the left mouse button. 2 years held it. Certainly "heavy" use, but it is too fast.
Spent a few days now, and it's a very good mouse. I only discovered after I bought it that it has an adjustable scroll wheel, so it was nice. You can turn a gadget on the bottom to make the scroll wheel click like normal scroll wheels, or you can make it "soft" like some Logitech mice have. However, it is not so heavy that you can "bounce" on it and make it roll for a while. Nice feature iaf.
The LEDs are the right standard now. Put mine on "cycling", so they change color a bit slowly. Looks nice, and doesn't bother.
It has an innovative new button called something special I already forgot. One that sits right in front of the thumb (see pictures), which also comes with a replaceable lever of different lengths. The longest lever was a little too long for me, but the intermediate variant fit perfectly.
Also has many, programmable, buttons! Definitely the best feature for me as I like to have a lot of shortcuts there. You have: The lever, 2 side buttons and 2 buttons behind the scroll wheel to program the best you want. Even the center button if you want. For me it will be 5 buttons iaf.
The fit is comfortable. It is normal sized and no monster such as Steelseries Rival 300, which I had before (was too big). Like the little rubber flare on which the thumb can rest.
In games, it performs well. I have a hard time feeling the difference in mice in games, so feel free to check out a more professional review for this particular area.
One problem * I * have with many modern mice is that M1 and M2 are pressed too easily, so you rest your hand, for example. M2 is pressed. This mouse was the best at all of the Razer, Logitech and Corsair mice I tested, which was about 10 in the same price range.
The software is a bit bloaty and a bit booky, but it doesn't bother me. You are in there so rarely anyway. You had to register for an account. reach the settings lol.