I've been tempted to give Canon the boot due to the banding problems I have encountered when lifting deep shadows (which seems to be necessary when shooting cityscapes at night with 11.7 stops of DR). My 5D II was awful and while my 5D III is better, its still a problem than needs fixing if I am to use the images for prints.
I have also become a bit tired of hearing people dismiss banding as evidence of 'file abuse' in post, so picked out an old shot that shows how banding is something that occurs in quite ordinary processing of certain files. I lifted the shadows and exposure as I might ordinarily process this file and then ran it though Dfine. The article can be found here.
If you have not use Dfine 2 and find banding a nuissance, but intend to stick with Canon (like me), then Nik Dfine is an absolute must have. Its certainly a heck of a lot cheaper (and less stressful) than switching out systems. Sony A7 and A7R bodies and Dfine are a good alternative!
Example before and after shown below, but bear in mind that it is much worse than this in full resolution print.