about the lifetime of batteries: I used it for 4 months on 800 dpi resolution with the GP batteries that came with he package. I am very pleased with the range (I used it in presentations ~ 7-8 meters distance).
Genius Traveler 915 is just about the size of a mobile phone. 2.4GHz digital cordless technology provides a longer range of working distance (up to 10 m) compared to traditional wireless devices, and delivers interference-free operation. The mini receiver stores inside of the mouse for easy transport and turns the mouse off for power efficiency. An advanced high precision 1600 dpi laser sensor can track on a variety of surfaces. The 4D-scrolling roller provides fast browsing in left, right, up and down on the Internet.