First up, this mouse feels very good. It's superbly smooth, more so than my previous Logitech G-series mice. The buttons are nice and very responsive, without being over sensitive (like the RMB on my G-600 that often gets activated merely by the weight of my finger resting on it). Shape-wise, it's a little large even for my large hands. But not so as to be uncomfortable, just … Large. I generally hate braided cables, never mind that they are fashionable. They tend to be stiff and the crinkle never goes out of them. This one is much softer, and it has no ‘hardwired’ kinks in it. Good job, Logitech. The scrollwheel is smooth as silk. Sadly, it does not appear to have the left and right tilt functions that used to be common on previous models. 3rd mouse button on the scrollwheel is still a mite too stiff to make it really useful, you just can't depress that wheel without moving the mouse around significantly as a side effect.
I had to download the latest version of the Logitech Gaming Software for the mouse to work properly. Even so, I have a small problem that, when I change between cordless and wired mode, there's some wait until the mouse gets recognized in the other mode, and at times I have to actively tinker and turn the Logitech software off, or unplug and reconnect the mouse until it works again (Windows 7 ultimate, 64bit). This may work more smoothly on Win 8.1 or 10, I have no idea yet since I haven't used it on the two other computers in the house.
Overall, a good mouse. I wanted to go wireless again after a long period of only using wired mice, and this is a success.