got mine yesterday and played a bit with it, very impressed! Still have to find a brick wall, but as far as I can tell everything is sharp. I'll still get the AF confirm chip (any recommendations? Found one on ebay that they can program to a fix EXIF (most seem to show a 50mm lens) so I'd have it set to 14mm and probably f8 I guess)
Mainly for very close focus handheld (meaning I can't really use live view and 10x magnification all that easy) as for landscape I set it between 1 and 2 feet, f5.6 or higher, everything sharp. No problems with vignetting either, even all the way open, very little flare, even with the sun in the image. Nice star shape for sun peeking through leaves at f22. Damn, this lens is wide! Love it so far. Hope I find time to take it to town today a bit.
edit to add: will mostly use this on 5D3 but also on 40D and what ever might come home in the coming years.