I cheat. My eyes are not as good as used to be and I am a bit color challenged. So, before making a serious photo (with tripod, and all), I make a reference photo carefully focussed at f/8 and containing a gray card. This becomes a reference image when I post process the real one.
I have not yet received my D800, but with my D700 images I can mitigate the effects of diffraction at f/16 and f/22. I find it far easier to evaluate my post processing efforts by comparing them to a reference rather than looking at a single image.
There seems to be a lot of extreme concern and hand wringing about diffraction with the D800 at f/11 and smaller aperture settings. I have used Jason O'Dell's sharpening techniques for a year or so and find them quite effective. Although I do not expect to totally eliminate the effects of diffraction with the D800, I absolutely refuse to give up on f/16 without a fight.