I own a few months ago, the Canon EF 17-40mm / 1: 4.0 L lens with which I, apart from the known problems of a wide-angle, am quite happy.
Both lenses were worn by the Canon EOS 5D Mark II.
As a special photo tour pending I've now thought that this lens here that Canon EF 16-35mm 1: 2.8L II, with a twice as high price indeed in any manner (except for the shutter 2,8er) better must be as my current.
In a nutshell, after more than 50 test / comparison images in JPEG format (no night scenes) (Freehand / tripod + self-timer) in the last few days I have to honestly say that on my monitor (HP w2408h) no and so I really do not mean! Differences For me to identify.
Sure, there may for professionals but otherwise ausschauen for me as an amateur is really only interested in landscapes, it makes no sense to keep / use this lens.
Solely the feel seems a little high but that does not justify the price (in my eyes).
Oh, and as crazy as it sounds, at 16mm and maximum aperture of blur in the image range is almost more than my Canon EF 17-40mm / 1: 4,0 L.