An update -
I now have two sets of sample images from two different 200-400/4 ED AIS users.
One from Wally of the telephone pole that showed to be not very sharp at 400mm f/4.
The second set by another user over on FM, taken of a line of distant trees against the skyline showed impressive sharpness wide open with little improvement stopping down, both at 200mm and 400mm settings. Contrast was a little low, but I can deal with that in post. Sharpness was not as good as my very best glass, but it was surprisingly good and equal to my (just now sold) 500/4 AI-P at f/5.6 and appears to be on par with my 400/5.6 ED-AI wide open.
I'd say it's just slightly better than my 180/4 Voigt APO for sharpness at f/4, but the Voigt has incredible contrast right from f/4.
So Wally - your sample images appeared to be a bit soft - maybe because the subject distance was pretty close and this lens does better at/near infinity?
Images later today.
- John