Everything positive you read about this lens is true.
The auto focus could be faster but it is not a show stopper.
I shoot dancers and acrobatics while they perform fast and complex moves in very low available light (wide open) without a problem. The auto focus is very accurate and fast enough.
In my opinion this lens is great for low light indoor sports. While it is not a forgiving lens, with the right technique this lens is amazing.
The lens balances perfectly on a 1d series camera.