I skived off this afternoon, to see what this lens can do. Nothing artistic. I had an hour to shoot some stuff in town with the 28-400. I like to test out new gear in real life situations. I have done some minor tweaking and some keystone correction. I did not find the aperture limiting in the old church. I just used a higher ISO. I did not find F8 limiting for this sort of photography.
On my big screen they look nice and sharp with lots of detail. I think optically it is better than the 24-200
Here are some examples.