IntelliEye Technology:

So you ask, what is this new improved "IntelliEye Optical Technology?" Microsoft was the developer for the first release of the IntelliEye Technology, and now they have released this new and improved version.

What's New?
Improved tracking speed - Using IntelliEye Technology, the mouse tracks up to 37 inches per second, meaning it will always keep up with your hand.

Increased accuracy - The new IntelliEye Technology provides superior accuracy and enables the cursor to land where you want it 100% of the time. With the IntelliEye Technology the sensor on the bottom of the mouse uses digital technology to track pointing device movement, so you experience greater pointing accuracy.

Consistent performance - The IntelliEye Technology there is no use for a ball or moving parts in your mouse to work, therefore it is easy to keep clean, and stays precise over time.

Works Everywhere - The IntelliEye Technology works on most surfaces, so you no longer need a mouse pad. Use it on your desk, the kitchen counter, or even your pant leg. With this technology it is best and recommended that you use it on surfaces with detail to track. It will not function on surfaces without visible detail (such as glass) or surfaces on which it has a reflection (such as mirrors or glossy surfaces.)