Odds are that there must be some considerable variances between IQ100's.
I personally don't see much improvement in DR over my CCD at base ISO, sorry, I wish I could say I did. I expected much more shadow recovery, then what I am seeing. Net 1 stop Max and many times not even 1 stop. This is at 50 and 100 (as they are pretty much the same from what I have read).
Was expecting to see more recovery like the Nikon D810 has, 2.5 stops at 64 ISO, fully useable. Not the case with my back, however as others are reporting that it can be done, I will assume that once I again, I more than likely purchased a bit early on the curve?
What I do see is that when exposed correctly, higher iso in the 200 to 800 range is very useable. By exposed correctly, I just mean not much push if anything slightly overexposed. This gives a very useable image. But push a 200 to 800 shot, can't be done way too much noise.
The CCD backs I have used even in good light still showed considerable saturation loss and some details lost in the 200 to 800 range. Unless sensor plus was in use.
I basically expose to the left with this back, as my back seems to recover highlights much forgivingly than pushing up shadows.
There is good comparison on LuLa by Wayne Fox showing a push from ISO 50, and the details,color, saturation that he still has, I can't get there with mine, as I have mightly tried. So odds are some fine tuning has been done since the first back.
Paul C