Actually, if I'm not wrong, the Razor Boomslang does use optical technology. However, rather than letting the optical sensor track the surface of the mousepad, it tracks the surface of the mouse ball. This provides consistency in the tracking surface - its always a mouse ball - compared to the mousepad, which will always be different depending on what you use. Also, and I'm just guessing here, that the fixing of the sensor and mouseball can also mean that the texture/surface of the mouseball can be optimized to allow for better optical tracking, and vice versa.