There is a lot of detailed information about this excellent gaming mouse, so I thought I would offer some plain English explanation of what I see as the mouse's appeal.
First, the textured surface helps you keep a super clear idea how you're holding the mouse, without looking away, and to not lose your grip on it during intense gameplay, which helps with accuracy, generally. This is supported by the overall shape of the mouse, including the rest for your thumb, on the left side of the mouse. Some users seem to think the mouse is on the small side; I disagree. It is the largest mouse I've owned in over 20 years.
The wheel adjusts to allow for easier scrolling, or, to offer more resistance while turning it -- again to increase accuracy while running through side menus swapping out weapons or whatever. The wheel makes a slight clicking when spun; To increase that tension, your adjustments (made underneath the mouse) make the wheel more audible-y "clicky." The overall impact is that of a very precise and expensive tool, like a surgical instrument.
On top of the mouse, the two buttons at the base of the wheel can be used to adjust the DPI, or in other words, how fast and far the cursor moves when you move the entire mouse. It is set so you can quickly change that during gameplay, and without looking at the mouse.
Mostly, though, I have to say, I think a major appeal of the mouse is the super cool, super vibrant color shifting which can be adjusted to continuously fade from one color to another. It is, actually, really cool effect. Works great, looks great, too.