The Logitech T631 is a well made and good looking mouse; with a smooth white plastic on top of a cool metal base. The mouse is small - its barely bigger than a credit card and about as thick as a mobile phone. It connects to your computer by bluetooth; and if you have a desktop its worth nothing there isn't a dongle in the packaging. On the base of the mouse is a connect button and for me a feature I asked logitech to add a number of years ago - a Computer 1/2 Switch. You can program the mouse to work with multiple computers - I have 3 on my desk today and being able to cut down on the mice on my desk is a great advantage. If you use the mouse with a desktop and notebook when you are on the road it will do the same for you. For those on the road the mouse charges from a USB micro cable; so if you have pretty much any phone bar an iPhone you already have the cable in your bag; Logitech include a tiny USB micro cable if you don't. Charging from USB is very convenient; though the battery seems to last at least 8 days between charging; the battery indicator on the control panel suggested it was getting low so i charged it at that point.
Logitech chose the shape is determined by its top surface being a touch surface and so its large and flat; my previous mouse the Logitech T620 Touch Mouse - Graphite
has the same touch features (albeit Windows 8 only) but is considerably larger - and considerably more comfortable to use as a mouse. The Touch functions allow you to control OSX functions like swipe on Safari or change desktops unfortunately they don't include the mouse pointer so you have to move the mouse to control the pointer and the T631 is just too small to use comfortably and that sadly detracts from everything else.
I love the charging, the ability to use with two computers and the touch functions but for general mouse pointer duty the T631 falls flat 3*.