I really hate the side-thumb button placement. It's exactly where I rest my thumb, and I keep clicking it with the edge of my thumb. It is a little too tall in the front for my hand style, and the battery didn't last even 12 hours (maybe because it wasn't fully charged?)
I am impressed by the lightness, it doesn't use batteries and is even lighter than my wired mice. Included accessories are nice, grip tape, 3x different feet types. Software works fine, lets you set DPIs so high that human hands couldn't possibly make any use of, you'd need the reactions of an insect.
Another note: I keep my hands VERY clean, and still even after less than 24hrs it already has some shine on it. Not a great sign.