However, the mouse works just fine with *one* battery! If you have to use this mouse, just leave one out. Being precise will very quickly give you a tired hand. All of the other current wireless mice from Microsoft make do with 1 AA, and the difference is huge. Experience fewer interuptions with up to 15 months of battery life for your keyboard. The wireless USB transceiver delivers a reliable wireless connection of up to 4.5 metres, with virtually no interference. You have to quickly learn to keep your fingers far away from this thing or else your view will be sliding around.The Weight - Running on two AA batteries means this mouse is heavy. Quickly access frequently used tools, like the calculator, zoom and audio controls by using shortcut keys. and if you so much as breathe on it you are scrolling. The sound when you actually click a button down is loud if you are ever trying to use a computer quietly, you don' t want to be using this.The Wheel - The mouse wheel is butter smooth. The shiny top plastic that forms the buttons feels cheap and thin, yet you have to press extra hard in order to click. For tracking performance, it is impossible to tell that this is not a standard wired mouse.The Bad:Build quality - This mouse feels worse than some 5 dollar generic. I tried to move to this mouse from a cheap MX310 and it felt like a huge step down.The Good:Performance - The wireless connection and BlueTrack sensor work flawlessly. The only way to describe this mouse: The latest and greatest technology wrapped in a dollar-store shell.If you want really want a wireless mouse, choose to spend a little more for solidly-built offering from Microsoft or Logitech.