Great, but limited for big hands.
The mouse is top-notch, very responsive, very good apparent quality, and the 'click' sensations are good.
In terms of design, it looks great with a keyboard from the same brand, and you can use the same colour scheme directly from the Razer application.
The only downside for me is that it's a bit small for big hands (I'm a size 10 in gloves for comparison). So for me, the best would have been 0.5cm longer and 1cm wider.