After a week of light use, I'm still having trouble getting the computer to know whether I mean left click or right click. I still wish they hadn't tried to be clever by having one switch for two buttons, and I still hope they fix this defect in later releases.
I like the usual Apple flat mouse shape. The last few years of orogeny in PC mice has just lead to uncomfortable mice, as far as I can tell.
I like the solid look more than the old "Perspex paperweight" look.
I love the nipple, perhaps because I was bottle-fed.
I keep seeing what I assume is a bug in the new mouse driver. Often – though I've not worked out the exact circumstances – I'll click to give focus to a window, but it won't get focus. It'll come to the front of the window stack, but it won't have the focus. So if I sweep-select some text, it'll sweep out in gray rather than blue. Clicking on stuff doesn't seem to work, either, until you've clicked in another window and then clicked back in the window you'd tried to give focus to.
Google tells me Microsoft still make white-ish scroll-wheel mice without arched backs. Maybe I should try one of them next, even if it means giving up on the nipple.