Nikon AF improvement?

I agree, running off a few quick shots with the d4 during a quick fast action subject such as a track hurdler or bif during the peak action is really needed with sports or bif.  The d4 is made for this.  I consider my upgrade from the d3s to the d4 a good upgrade for the type of shooting I do.  For me there was a learning curve using the af on the d4, but after several months the d4 hits the focus right on.

Larry