Ergonomically, this is a vey nice mouse. I don't like the small kind because they end up making my hand feel cramped. This one is a nice full size and has sort of 'wings' on the sides to rest your thumb and ring finger.
It has back and forward buttons for browsers and a dpi setting button on top. The mouse moves and scrolls smoothly, clicks very quietly and is rechargeable -- no more replacing batteries over and over. It works with bluetooth wireless or you can plug in the usb dongle for it to work that way. It has an on/off button and it goes to sleep when you're not using it.
Overall, it's the best quiet full size mouse I've found. Highly recommended.