I'm not as happy with this lens as a lot of other people are here. I use it with my 7D and I find it too soft below 5.6 to be useful. I wanted this lens because it's fast, but at 2.8 it's unacceptable, way too soft. It's noticeably sharper and OK at around 4.0 and better at 5.0, but I cringe whenever I go below 5.6. For the money I expected more. The newer model is supposed to be an improvement, but it's $1,000 more.
Problems:
Too soft below 5.6 and unusable at 2.8.
Problems:
Too soft below 5.6 and unusable at 2.8.