Finally, I got my long awaited Nikon D4. I made my booking when Nikon announced it's open for booking. As I always pay more attention on ISO performance, I did some reading on it's pre-production review comparison. It claimed that the ISO is better by 1 stop or 1.5 stop. However it is not the case after some test run when I got the camera. Yes, there is improvement, but not 1 stop as people claimed. I would say maybe 1/3 better. But one thing that impressed me is the fast focusing system, much faster and accurate then D3s. The image quality and details produced is simply amazing. The continuous tracking system is awesome as well. Needless to say, I still need time explorin and getting used to some of the settings.