Conclusion: Great value, the version II brought the price of the older version down. Was nice on the APS-C 1.6x crop 7D. Pretty sharp, shot mostly at f2.8 unless I was doing some architectural work. Fast, wide, creates some fun images.
Pros: Wide wide wide. Sharp. Fast.
Cons: Lots of distortion, good amount of vignetting.
Conclusion: This is one of my favourite lenses. Build quality is very good, along with IQ and versatility. I've recently sold this lens as I needed the funds for dedicated portrait lens due to my changing photographic style. It was such a hard decision, and do miss it for some of it's unique qualities. I will defiantly buy this or the mark 2 version again when funds allow! I used this lens on a full frame body, mainly for landscapes and photojournalist work.
Pros: Build quality, IQ, Focal length, sharpness, light but well built, great walk about lens.
Cons: Very soft around the edges at 2.8 on a full frame body!
Conclusion: This was my first Canon "L" series lens. I am using it now on a Canon 60D, with an APS-C sensor. So far, I am very pleased with the results. I can't wait to try it on a camera with a full frame sensor. It blows the other lenses I have out of the water, and this is now the lens I use most frequently. I love the sharpness and quickness of the autofocus. It is very good in low light, and the lack of IS is not missed.
Pros: Quick, accurate auto-focus, good contrast, good colour, nice bokeh.
Summary: If you can afford the MKII version of this lens, then go for it; but otherwise, if you're a HDSLR video shooter like I am, get this lens and save yourself a couple bucks. The image quality is vibrant and sharp and looks fantastic. Being able to stop down to F/2.8 at 16mm is fantastic, and the focal length is great too. I would highly recommend this for photography as well (as it is originally intended). It's a Canon L lens, my favorite one besides the 35mm F/1.4 prime.
Conclusion: Overall a very good lens--my first L lens, which I have now owned for approximately than five years. I chose this lens because of its focal length range, maximum aperture, and focal length. I also like the fact that it uses a 77mm threaded filter. Images are crisp and sharp, and colors are always wonderful. At 35mm is doesn't perform as well as the Canon EF 35mm f/1.4L USM, but you wouldn't expect it too since it is a zoom lens.
Pros: Overall very sharp, great color rendition, & super fast--everything you would expect from a L-lens.
Cons: Corners are a little soft when used wide open (f/2.8), especially on extra large sensors (5D Mark II--but not so bad on 5D Mark I).