The new shape is even more relaxing to grip and fits the hand even better than before. A larger lip better supports the last finger. 
A pointer speed button behind the wheel allows convenient adjustment without even changing your grip on the mouse. Top mounted LEDs indicate selected pointer speed from low to high 
Pure eye candy. The illumination flashes briefly only during power on and when changing pointer speed. 
The tiny 2.4 GHz receiver avoids being knocked off the side of a notebook computer. (Windows and Mac compatible.) 
Mouse Manager software enables configuring 5 buttons for performing many actions without moving the mouse or touching the keyboard.