Last week I was able to go shoot for myself for about 30 minutes or so before a freelance job. The new Canon 5Ds was a simple transition from the Mark III. The camera feels and acts just like my Mark III that I just sold. The big difference is going from 21 mega Pixels to 50 mega pixels. In many was 50 pixels is not needed unless I decide to crop in on an image. If I crop in to now only show 50% of an image I will be showing 25 mega pixels. Yes sharper than the Mark III.
Another way to look at it, if I shoot with my 300mm lens with my 2x tel. on and I crop in tighter, I'm at 1200mm . Way cool!
More testing to come.