

At first I wasn't so happy with it coming off of the ultra high DPI Microsoft/Razer Habu, although it has a ton more useful features. Then Matlock pointed me to a hacked driver that makes everything happy. This mouse is fucking incredible. INCREDIBLE!!!!!!!
7 buttons, all configurable to do extremely specific tasks. 2 scroll wheels (the side scroll wheel is for using flip3d in vista, or alt-tabbing between windows in XP.
The SmartShift technolgy behind the mouse wheel on top is no hype, either. It turns from a clicky mouse wheel to a fast, smooth, no clicky mouse wheel depending on the application.
The software is pretty great, and you can take configurations to a granular level, giving it separate configurations for different apps, or even different windows in the same app (in some cases).