Edges are fine. Extreme corners see a little weirdness, but it looks more like the usual ultrawide distortion/stretching rather than softness or field curvature. AF is as good as any other lens, though I haven't given it anything particularly taxing - I suspect it will be as good as any body allows it to be.
I may be the wrong guy to ask though. I rarely do ultrawide work, so this will just sit in my bag except for the 2-3 times a year i might need it. As such, I'm probably not as discerning as somebody who's bread and butter is ultrawide landscapes.