The D4 video in 2.7x crop mode is REALLY sharp and useful. In the FX mode (using 100% of the sensor) I found I need sharpening post processing using Adober Premiere Pro. I did not need such sharpening using the 5D mkII. However where the D4 video really excel is with its low light performance couple with a good metering system, shooting low light movies turn out to be really good.
I did not compare one to one the D4 and the 5D mkIII video, but I will do so with my upcoming 1DX!