I chose this mouse because of the extra support it provides for ring finger and pinky, and because it has plenty of buttons. I got it for work, not so much for gaming. I think it's important to have a comfortable mouse if you're going to be using it all day every day.
With every other mouse I've tried I get a sore hand by the end of the day, but not with this mouse. It's supremely comfortable, and fits my hand perfectly, providing support for all the fingers. It's quite a bit wider than most other mouses and is not too tall unlike some others (cough...logitech...) It's lightweight, glides smoothly across the desk, and the accuracy is every bit as good as any other gaming mouse I've tried.
The only thing I don't like about it is that it has only 9 buttons. My previous mouse had 12 and I used to use 10 of those all the time (counting wheel-up and -down). Not a big deal - I remapped the "forward" thumb button to F5 "reload the web page" easily using the software provided.
In short - best mouse I've ever used.
UPDATE - this mouse really needs a mousepad to track properly. I was using it on a white melamine desk and it would frequently lose tracking, as if there was dust or fluff inside the sensor. I must have looked a right 'nana to my co-workers, always blowing imaginary dust out of the bottom of my fancy mouse! Since then I've got a mousepad for it, and it hasn't missed a beat since then.