Those who read the "printers, papers & inks" forum may know that, besides being a photographer, I run a fine art printing studio, printing for several photographers and digital artists from all over the world.
One of the advantages of my work is that I am required to handle, adjust and print files produced with all existing cameras and lenses. Plus, we usually print big (24x36", 36x54", 44x66") and that gives me the chance to evaluate the printed result of the files produced by those cameras/lenses. Sure we cannot make direct comparisons as the subjects and photographers are different, but after a couple of dozen files we can get a general idea about the output quality of that specific equipment.
Last Friday I downloaded and printed one of the full resolution files from the 5Ds. I printed a crop, a strip of 8x40" from what would be a uncropped 40x60" print. Almost no adjustment, black point and white point adjustments and the print sharpening. Although it was a JPEG file and the photo was taken with a zoom lens (24-70mm f:2.8 II) the resulting print is nothing short of amazing for a 35mm DSLR. Not even a D810 with an Ottus can render that level of detail when printed at that size.
It is impossible to judge things like DR without a detailed side by side comparison and is dangerous to form an opinion based on a single example, but from the resolution and detail perspective I can assure you the 5Ds will be perfect for those who want to print big. Very clean files even on the shadows, but as it was a JPEG file we cannot say for sure that it is not due to an efficient noise reduction.