I got this lens in late October with the dock.
Right out of the box I took it to shoot at a night football game.
Pictures were a disappointment. Lots of soft pictures or out of focus.
Did the focus adjust with the dock and the pictures were like night and day.
I have a 300mm 2.8 L non IS to compare this lens to.
The speed of the focus tracking I don't think is as good as the Canon's.
I do find I have a few more out of focus pictures the normal.
If you have non fast moving subject the lens works pretty good.
The image quality with this lens is excellent.
I mainly used this lens for sports.
So far I used it for football, soccer and basketball.
Here are a few samples.
Body used is a 1DMK4
I think all shot at 2.8
All the pictures have sharpening during post processing .