Software

The MM520 has one of the best mouse drivers I have ever used. It is very lightweight, only eating up 0.9 MB of memory in the background, and needs around 91 MB of disk space. There are lots of options to choose from; you can set the CPI, polling rate, LOD, and key assignments. You can create macros, profiles, and can play with the lighting. More on the latter below.

Lighting

I would say the picture says it all, but that would be a lie. There are so many options to choose from, it's really amazing. I am not a fan of RGB or any kind of lighting myself, but Cooler Master has played the eye candy part extremely well. There are three zones that are perfectly and individually programmable. These three zones are the scroll wheel, CM logo, and a line at the bottom of the back.

I recorded a video as well, though it looks much better in person and only conveys the lighting capabilities a bit: