Absolutely lovely! Both the BW and colour versions are great.Eldar, I'd rather be shown than assured.I got the 200-400 f4L IS 1.4x for sports and wildlife. For this purpose I believe it is the ultimate lens (at the moment).
My particular interest is in bird photography, which is one of the fields in which the 200-400mm is being touted as ideal.
So far, the bird images I've seen taken with this lens all have that 'zoom lens look', lacking the crispness, contrast, colour rendition and bokeh of a high quality prime.
In my experience of reviewing hundreds of thousands of bird images online, these qualities are visible even at web sizes.
If you had to make a living shooting bird images, would you seriously choose your 200-400mm over a 500mm or 600mm prime?
For birds I prefer the 600 f4L IS II, often combined with the 1.4xIII extender. But that is not because of optical quality, but for reach. I had the 400mm f2.8L IS II also earlier, but I sold it a while after I got the 200-400, because it is that good. But the 600 stays, because it is a phenomenal lens and it covers a different need.
I don´t know what it takes to convince you, but I have attached the color version of my avatar, shot with a 1DX at 560mm, f5.6, 1/200s and ISO400.