Some will argue it's about AF performance/problems.. but for me, the images in medium to low light are where the differences really are apparent. Mark 3 has a significant improvement in high ISO noise and color tonality. I find that the 14bit files give me much more room for adjustments and recovery when shooting raw over my MkIIN files. My MKIII was purchased in July and has not had the submirror fix. I was one of the lucky ones apparently as I have had great luck so far...Definitely the favorite body that I have ever used.
If I get a chance, I'll see if I have any comparable images to share. I sold my MkIIN a few months ago, so I can't do any side by side testing right now.
I had the mark2 n and now the mark3. To me the mark2n images were nice, but no comparison to the mark3. The files are a joy to work with if you shoot raw. Better noise and richness of the files as far as contrast and color. Its hard to explain, but it is easier to get the images to pop without them falling apart with the mark3. I was so impressed I am considering the 1DS mark3. Canon made some real improvements in the IQ area with this one.
