Thanks for the feedback, erpman and Tony
I assume Briot's digiback did not have an AA filter, and the 45MP digiback he used likely had a pixel size of ~6 microns. The D800 pixel size is ~4.9 microns. I appreciate the medium format systems will likely perform better at smaller apertures given the larger pixel size when compared to something in the ballpark of a DSLR FX like the D800. I once read the ideal pixel size is around 6 microns based on work done by Leica when the S2 was released. I have not read much about pixel size relative to diffraction softening. Pixel size discussions are more often about high ISO noise reduction. With the D800 pushing pixel size limitations to the extreme, diffraction issues could become more evident based on what I am reading and the reason why I was compelled to join this discussion. From what I am gathering, for purposes of printing and maintaining DOF, I'll be fine shooting apertures as small as f16, but I'll do my best to shoot wider when appropriate.
This brings me back to the subject of lenses, I also appreciate DOF is something much easier to accomplish with wider lenses. I don't like getting too wide... over the years I have found my "sweet spot" is shooting around 40 to 45MM focal lengths. Subsequently, I began getting rid of my zoom lenses for landscape work in an effort towards improving print quality... no more ugly chromatic aberrations and serious lens flare issues! I stuck with Zeiss glass for Nikon (even if it is made in Japan, the quality of build is superior to Nikon's). Then I tried Nikon's 45MM PC-E and I was hooked with the convenience of fine tuning landscape compositions without having to move the tripod in difficult terrain by using the shift movements. I also gained the opportunity to produce better files for stitching if desired, although I have yet to take much advantage of stitching and most of my landscape work does no lend itself to tilting. Another advantage or the tilt-shift lenses is they serve reasonably well for macro. For me, tilt-shift lenses offer the most in terms creative possibilities, I'll never outgrow all of the options one can explore.
Although the Nikon 45MM PC-E glass is outstanding, the build quality has something to be desired... it is too loose with tilt and shift movements, subsequently I desired a better build quality. Nikon brags about how their PC-E lenses have rubber O-rings, but what good is the O-ring with loose fitting tilt and shift movements? While cost is a serious limiting consideration for 99% of us, it is clearly evident that we get what we pay for when it comes to lens quality.
Eventually, my search for the perfect lens settled on Hartblei Superrotators. Their 40MM model is perfect for my style of shooting, the glass is German made ("TRUE" Carl Zeiss glass) even if the barrel and assembly is Ukrainian. I put the Hartblei 4/40 IF TS Superrotator on my wish list two years ago. When the D800E was released, I figured it was time to bite the bullet and buy one. Stefan has my hard-earned money and I'll soon have one of his lenses.