Running only 20MP from a FF sensor is one way to get good low-light performance. It also lets you get high FPS numbers. I'm most impressed by the 4k@60FPS video mode; last I checked that was a RED thing (or GoPro, but you know what I mean).
I came here to say exactly this. I'm impressed with what is offered for the 4K video and if the price holds true at $6K I'm rather impressed on paper. Real world may prove otherwise.