Soooooo........ This showed up at my house a couple of weeks ago. I finally ordered it in mid-August after pouring over many video reviews.
I've been playing around with it and trying different settings, and so far I'm really impressed. For myself, as a bird/wildlife shooter mostly, I was mainly intrigued by the new eye specific focus system. I have to say that so far I am happy with how it works. Once it finds the eye of the animal, it stays locked on it, greatly increasing the keeper rate.
I find the electronic shutter quite useful also, especially if I am within earshot of my target. It is pretty much silent when shooting the 20fps it is capable of. Before with my other cameras, the clunking of the mirror slapping up and down would often frighten my subject. Even the mechanical shutter on this camera is much quieter.
Low light capability is also greatly improved. Canon seems to have made some huge inroads in that regard. In some instances I have taken shots at 12,800ISO that were quite usable with no extra processing, even when cropped significantly. 25,600ISO is not out of the question for many applications, especially with some of the denoise plugins available now.
Going from a traditional DSLR to a mirrorless system, I was a bit apprehensive at first. But the transition has been pretty seamless for the most part. The level of customization on this camera is top notch, as is typical for Canon's upper end cameras.