Hm, looks like my 24-70mm lens needs to do (undo?) some autofocus micro adujstment. Not that you can tell here. Also an illustration of how the (unmodded) 5DIII's dynamic range isn't great, but nevertheless usable. Which reminds me there is now a beta hack from Magic Lantern that expands the 5DIII's dynamic range by about 2 stops...I'll wait for a few more rounds to try it out, I'm conservative enought not to put a new beta build on my good camera. Nightly builds themselves are here.
Update #1: redid the autofocus micro adjustment on the 24-70mm f/2.8 on the long end, moved from -12 to -2. Def. wrong as it was. Oh well.