The bottom line of this for me is a) why should I keep the 2.8 when I could probably sell if for 2k? I am not sure I see when or why I would prefer to use it given the performance of this latest f/4.0. In all of the comparisons I posted it appears that the f4.0 is producing at least as good quality image as the 2.8, whether in low light, hand held, tripod or outdoor and in good light.
b)I already gave away my 24-70/2.8 because I have come to rely on my 24-120/f4. So, it seems that Nikon has done such a terrific job with these new, less expensive, f4.0 series that they are making obsolete there more expensive series.
We really should congratulate Nikon on their improvement in optics technology.