I love this mouse. It fits my medium small hand comfortably and is great on battery life so far. It's not overly responsive and jerky like lasers seem to be. This one gives me very smooth performance.
It has a "shut off" tab under the mouse belly, but if you slide the USB key into it, it also shuts it off. If you hibernate it shuts off, but immediately turns back on when your computer does. I like the rubberized finger and palm areas much better than my Microsoft Wireless Notebook Laser Mouse 6000. The only drawback is that this wireless notebook unit doesnt have thumb button and that's why I ended up buying the Microsoft 6000. I miss that particular feature. Funny think is though, I seem to use the Kensington 90% of the time anyway. The M6000 is lighter since it only uses 1 battery, but it chews through them like crazy, and my hand just doesnt feel comfortable in the curved finger slots and palm rest, the grip area seem slippery, and since it's a laser, is a little to sensative for my taste. I also like the Kensington's center scroll button musch better. It clicks with each finger movement, where the Microsoft is a smooth rolling and you tend to overshoot when you scroll. That's why I keep going back to the Kensington.
You can go to Kensington's site and download their software if you want to. Otherwise, just insert the two batteries ( I like how they are hidden) plug in the USB key and off you go.
I would recommend this product and purchase it again in a heartbeat.
ONE FINAL NOTE.... everyone who complains about lack of distance/reception
must be plugging the USB key into the back of their laptops. I have mine plugged into the side port and can still get reception from 10 feet away. Plugged into the back....I might get 3 feet. But who cares... how far away from the screen are you when you use your mouse? A couple inches???