After reading this thread I went home and shot a few images of focus charts. Just as Nasim recommends, I shot a reference image using live view, zoomed in, depressed shutter half way to lock in focus (using a cable release) and took the image. Then I shot 3-4 more images not using live view, but similarly depressing release half way to lock focus. The images were similar to the reference image.
Unlike other of the posters here, I can't say that it was a BANG moment of unbelieveable sharpness. All images, when zoomed into 100%, were reasonable. If you look at Nasim's site and the images of the test chart, the one he refers to as acceptably focused is about the same as the one I got, which is not razor sharp focus.
I guess all of this is to say that I'm now questioning my own judgment of what constitutes acceptable spot-on sharpness.
For the sake of comparison, using the same lens and the same shooting set up, I took the same series of test images using my D300s and the reference image and subsequent images were all of about the same sharpness as with my D4. Does this mean that my autofocus is spot on? This thread has me second guessing my judgments, that's for sure.
I'll keep reading and assessing. I surely don't want to send back my D4 without feeling certain that it needs tuning.