Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Best mouse of its kind

I've used several optical mice over the years, and this one beats them all. The buttons are all programmable and while the software doesn't let you configure the buttons/acceleration/speed to the extent that Kensington does, the shape of the mouse is very comfortable (for righties only). If you want a symmetric mouse or more programmability try Kensington's mice.