Happy to report I have zero picture issues with my (ISF pro calibrated) 75Z9D which arrived this morning.
I spend nearly 2 hours taking a critical look while playing all sorts of content (2D/3D SDR as well as 4K/HDR) I'm familiar with and I was actually looking for problems. I have zero banding (either vertical or horizontal) on this set. I had obvious vertical banding with 3D on my X940D but fortunately none on the 75Z9D. 3D is great btw but I did had to reboot the TV in order to get rid of excessive ghosting and flickering in only the lower half of the screen. Very odd but it's gone now.
Also no more annoying horizontal lines during HDR playback (which was my biggest issue with the X940D)! That is such a relief, I am so glad I don't have to look at that anymore now!!! Those days are finally over now.
Will have to try some test patterns some other time but at first sight, I didn't notice any DSE. I had some on my X940D (and to an even lesser extend on my 65Z9D) but nothing really too serious. I then took a look at all four corners and even on the main menu screen of the Nintendo Switch, I could hardly make out if they were slightly darker or not.
As I was watching clips form various movies I had the feeling as if it looked just a tad sharper and more refined. But I couldn't honestly say if that really was the case or the placebo effect. I still have my X940D until Sony comes by and collect it. Just for fun I might put it side to side with the 75Z9D and play the exact same content on both TVs and take a look at the difference.
As on my 65Z9, I did notice that when something really bright is near the black borders of scope movies during HDR, they would become just a tad less black than they normally would be for a second or two. But this would only be really noticable if you had your eyes on the black borders all the time.
Anyway I am really glad I won the panel lottery again (my 65Z9D is 99% free of screen issues, it only has very slight DSE) and was still able to get a 75Z9D in the first place. The 65Z9D is still widely available in my country but the 75Z9D has become almost absolete it seems.
Now comes the task of disabling/removing as much of the spyware stuff etc...