My new 5D MK III came last night, I played with it a bit, but to get the best sharpness, I need to AFMA my lenses.
So, for a sharpness test, I tethered the camera to a pc, with my 100mm L macro and took two shots that were focused using live focus, which is usually about as good as you can get. focus point was the AF / MA switch.
One image at f/2.8 and one at f/5.6. Then, I cropped the focus point to 100%.
I converted the raw images to dng using Adobe DNG converter 6.7 Release Candidate 1
The results were sharp as expected.
100mm L at f/2.8 ISO 100 (1/80 sec for f/2.8 and 1/25 sec for f/5.6) Sharpening and NA set to zero, but lens correction and CA removal was on. I don't see that they need sharpening.
100mm L at 5/5.6