I think that one point is missed by the argument that we are "trapeed" by investment is Canon glass. Personally, I don't feel trapped at all. One of the biggest reasons I shoot Canon is in fact their lens selection. And the bottom line is that for me the D800 doesn't offer anything worth missing on the 50 1.2, 85 1.2 and MPE65 for example. Regardless of price. And I am positive that many feel the same.
you are making a good point here.
On the other hand ... I might actually prefer the new Nikon AF-S 50/1.4 over the Canon 50/1.2.
And the 85/1.2 II is a Canon treat, but the Nikon 85/1.4 is no slouch either.
As for the MPE65 I don't know whether or not there is a Nikon equivalent.
But there is no equivalent Canon WA-zoom (or prime) to compete with the Nikon 14-24. The 16-35 does not even come close. It remains to be seen whether the new Canon prime 24mm/2.8 will beat the Nikon zoom and if so, by how much.
The new Canon 24-70 II may be better than the current Nikon 24-70, which is slightly better than the current Canon version. And the Canon 70-200 2.8 L IS II is slightly better than the Nikon which seems to sufffer fairly heavily from lens breathing.
The two lens types where Canon has the upper hand are the new super-Teles and the new TS-E lenses (17/4, 24/2.
. Worse still, on the D800 the Nikon PCs tilt-shifts won't even work (!) - due to extremely poor design they will not clear the D800 body when trying to shift them upwards. -o-O-
So mileage will vary, depending on lenses needed and used.