6 out of 10 points and recommendedVery sharp, fastish auto-focushorible front focusing.
Initial results were disappointing. A line of trees was a blur. A second look showed that the grass in front of them was sharp. I was a victim of the dreaded Sigma front focus.reviewed July 6th, 2010
Mercifully I had a canon 50D, and a full +20 of microfocus adjustment solved the problem, although I could have done with a bit more.
My new 7D with +20 seems better. When I focus on a tree the front leaves are perfect as before, but the back leaves are better. A bit of back focus? If so I like it. You may be focusing on the front of a duck, but you are hoping that all of it will be sharp, and even on a duck the range of perfect focus is a few cm. On a dragonfly it is a fraction of a mm. Sigh.
The 7D autofocus can get confused. When moving from focusing on a dragonfly to a distant shot of a swan it just gave up! This is when the full time manual autofocus comes in. The shift from macro to teli is best done by hand. One quick turn and then let the autofocus take over. It's very fast if it doesn't have to travel far.
I love this lens. It is mostly the focal length. The flowers that I didn't have to stoop for, or trespass over flower bed borders. The dragonflies that didn't notice. The close up of a duck with 6 fluffy ducklings (a 100% crop of the ducklings showed no noticeable blur).
The speed of focus that let me catch a fleeing grass snake (swimming on the Thames) made my day!
This is going to be my number 1 lens until such time as somebody produces an affordable macro with the same sharpness and fast focusing with ether significantly longer focal length or image stabilization. It could be a long wait.