A Canon shooter has posted some D3 test pictures made during a trip to Sabi Sand. He states:

 “Well let me tell you something. It was the first time in my life that I shot a photo at ISO 25600. Yes you have seen it correctly. The shot with the lion stretching was done in near darkness. A photo I would never have taken.”

and further about the AF:

“I must say the Autofocus worked effortlessly between those grasses and twigs. It picked the leopard up with ease and kept the focus on it”

Note: the thread contains 100% crops, too, just scroll a bit…