Hi,
I compared the D800E with Landscape Sharpening to the Pentax 645D using one of the Iamging Resource test images, also with LS sharpening.
In my view the Pentax 645D clearly comes out on top, at least regarding LW/PH at 50% MTF. I'd guess the Pentax is much more Moiré prone than the D800E from the MTFs.
Pentax 645: 5348 LW/PH
Nikon D800E: 4035 LW/PH
So my take is that D800E may be mighty, but at least for resolution MF still has a handsome lead. Real world performance may be different, though. I have seen a comparison between Leica S2 and Nikon D800 by Diglloyd where I would give the nod to the D800. But the numbers speak for the Pentax 645D, unless you object to aliasing.
On the other hand, the Pentax 645D is low end in MF, cameras like the IQ180 would have smaller sensor pitch and be less prone to Moiré.
Best regards
Erik