There was a banding image up for a few days sorry I pulled it down. If you're interested I can try and get a variety of cropped isos put together for you if i get the time over the weekend In the end:
When went back to the store to return the unit and the canon dealer was intrigued (as you can see the banding on the back lcd as clear as day) He then got out the loaner unit and whilst it is still visible on the back lcd screen it wasn't anywhere near as bad as mine and the are sending that one back as a lemon.
We put both bodies through a battery of tests, shooting with the same then different lenses - all L's for the record - both units exhibited near same banding.It's very easy to replicate shoot dark grey to mid grey target or shoot a scene where there is shadows and it is visible in the shadows/dark greys. I never tried i but if my process holds true, shooting the night sky would yield the same result even more-so around dusk.
I am waiting to hear from Canon if there is actually a known issue with the processing engine/noise profile. It would explain why there is colour-bleeds visible in the raws on both the 1DX and 5D3, (and more then likely the real reason for the delay of the 1DX).
As previously noted - if you are using LR4, it automatically removes banding that occurs iso 100-3200 as the NR color slider is locked at 25 to begin with. cr2->dng->LR4 yields better results overall then cr2->dpp->tiff in my experience.
the latest dpp seems to ruin the image with unsharpen mask added by default ? (im not really a heavy user of dpp so im not the best when it comes to understanding why) artifacts are present in the image that aren't seen when converted to DNG.