haven't seen Casey's footage. However, I did watch the DigitalRev quick review and they actually did a comparison between the P4 and the MP cameras. The P4 is visibly sharper--they speculate it is due to the relatively smaller sensor in the MP.
Overall picture quality is good imho. I'm selling my P3 and ordered the MP yesterday. portability and general image quality etc. outweighs potentially better flight and camera performance of 4K phantoms.. but I'm all about run-and-gun. This is EXACTLY what i was looking for when i got into aerial camera platforms.
...my only concern is how long it's going to take to release some decent ND filters for this thing.