Summary: This lens seems to be really solid. I like the zoom range. The extremely wide angle of 16mm is necessary at times, but like all wide angles you get distortion which is the nature of the beast. So I really like 20mm because it reduces some of that.
Summary: I chose this lens for my 7D over the 16-35 II and the much-loved EF-S 17-55. The 16-35 II is obviously way more expensive. I chose it over the 17-55 due to the build quality and the extra mm, I already have the 36-55 range covered at 2.8, and the fact that I found an amazing deal on it.
Summary: Great wide angle lens, definite improvement over older EF 17-35 F2.8. All metal body, smooth, fast, quiet operation, better optics than 17-40. Great value compared to 16-35 F2.8L II. Of these four Canon wide angle lenses this one has the best cost/performance bang for the buck.
Summary: great lens. i got mine used and my only gripe about it is that it feels like there is a 'grain of sand' in the mechanism. it doesn't affect performance at all. i only notice it if i take the zoom to either extreme and then turn the focus ring further.
Summary: Personally, I think these "L" lenses are overrated and overpriced. Sure, they deliver better and sharper images and nice blurry backgrounds than the non "L" lenses shooting in well lighted conditions.
Summary: I'm a wedding photographer and own this lens (Version 1) plus the 24-70 f2.8 L. In my opinion, this lens is sharper than 24-70 in the middle part of the image. I can understand the vignetting for this kind of ultra wide angle lens but the flare is quite severe and the softening on the sides is not...
Conclusion: A zoom that I had more than 10 years. Despite its weakness in unsharp corners and poor flare performance, the zoom provides convinience and reliability when it comes to travel photography. My image gallery of 16-35/2.8 http://www.roentarre.com/Gallery.aspx?
Conclusion: As it is always: you get what you pay for. And if you buy this lens, you know what you want and you get what you want. On a documentary, this is the lens I would use straight out of the bag. It is good for sports because it has the two key facts: F2.8 and a fast focus.
Conclusion: My copy is second hand. I noticed immediately that it is very soft at 35mm - softer than any of my other L zooms such as 24-70L, 24-105L, 70-200L f/2.8 IS. Stopping down to f/5.6 or f/8 does not help much.