The battery compartment is on the top of the mouse, under the logo and where your palm rests, which was unexpected but I think it is a cute feature. The batteries are supposed to last up to three years but I would guess with daily use it might not last that long. Time will tell. The "Unifying receiver", which plugs into the USB port, can be stored in the battery compartment when not in use. Very handy.
The feel of the mouse is very nice. The top two button and palm areas are slick whereas the sides provide texture so you can grip it easily. The scroll wheel works beautifully. You can tilt it to the right to move forward one page while you're on an internet page and if you push the wheel to the left, you go back a page. I can get used to this! It also has a "middle button" which functions differently depending on your OS and the application you are using.
The "Unifying receiver" is small yet it can connect multiple Unifying compatible devices. I like this mouse. Now hopefully I won't misplace it!
I received this mouse for free from being in the Amazon Vine Program. No other compensation was received or expected.