As I decided to buy a 100-400 L for wildlife photos and as I travel a lot, I needed a complement to my 28-75 2.8 for street portraits and a lot more. I started to investigate on 135 f2, 70-200 L (IS or non)... after a long period of tests, I was amazed by its regular astonishing quality (various samples of each lens tested)... even better than the 135 f2!... yes, I remarked this.
According to all my requierements, it came on the top of the list.
In "close" distances, it is really incredibly good.
In longer ones, you may notice, at FULL SCREEN preview, a very very little subtle drop in quality, but "closing" a little the diaphragm, it becomes perfect.
You can search in the corners... they look like the center.
Contrast, colors? Is it a joke? WAOU!!