Really? Because the improvements from the mkII to the mkIII seemed fairly hu-hum for the most part. Then again...everything is relative.
My guess is midphase has not shot the 5DII and 5DIII, just looked at the features list. I shot the 5DII for 2+ years & have had the 5DIII for one year. It is much better in almost every respect based on the results I am getting. The colors are more vivid, the images are sharper, and the noise is lower. Also these features make a huge difference in the field, in no particular order:
much clearer LCD screen for live view or review of image quality
5 stop exposure compensation (5DII has 2 stops max)
Ability to shoot 7 shots for bracketing - max is 3 on the 5DII
Two cards (CF & SD) for storage of images
Slightly more megapixels for more room to crop (this isn't a huge difference)
6 frames per second vs. 4 fps on the 5DII for wildlife, etc.
Multiple exposure capability for landscapes & other applications
In-camera HDR if that's your thing (it's not mine as it still doesn't save the final image in RAW)
Better auto-focus by a bunch
All in all, it's a much better camera, as expected. I know this is only one person's opinion, but mine is a hands on experience for both cameras.