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. I am not an expert when it comes down to the technicalities of lenses, but there is some fuzziness in the corners apparent at large apertures. At the 16mm range of the lens, there is a lot of distortion, but this shows up in my other lens as well. I had compared this lens to the EF 35mm f/1.4 L lens, and thought I would get more use out of this lens. I am happy with my decision.
The manual for the lens specifies that it needs a filter to completely seal the lens. These tend to be expensive, but what do you expect when you need a 82mm filter size.