I've seen some semi-real-world results (deliberate test subjects) showing the D800 pretty close to the 40 mp generation MFDBs (which are not only lower resolution than the IQ180, but also older sensor generations). They are close enough that I wouldn't be surprised if the D800e reaches P45+ quality levels. I'll be very interested to see images that are not just tests, and to examine large prints - pixel peeping any of this stuff on screen is crazy because no monitor displays more than (rarely) 2560x1600 pixels!
The D3x was a close competitor to 20+ mp backs (another generation older), suggesting that FF sensors may just about keep up with MF sensors at the same resolution (obviously, except for depth of field and other direct effects of sensor size) because the extra generations of sensor development in the years it takes FF to reach a given resolution more or less cancel out the effect of pixel size? The newest generation MF sensors will always be significantly ahead, but at a high price. We seem to have the same generational effect with the (APS-C) NEX-7 possibly catching the D3x (or coming closer than one might think) - the 3 years newer sensor makes up for the smaller size... Of course, the NEX-7 has lens issues - Sony's built a camera their lenses don't always keep up with... They aren't alone, hasn't Phase had that problem with some of the older Mamiya lenses?
I wonder why no MFDB has gone CMOS? A double-size D800E sensor might be much cheaper to produce than the IQ180 sensor, and perhaps as good?