I have a pre-order on the 1D X, but might cancel and switch.
As you may know this body only has an estimated price of 6500,- euro's.
The 1D X outperforms the D800 in:
- ISO (most probably)
- Speed
- Robustness
As the main differentiators.
If these things are important to you then the 1D X will be a good camera.
If ISO, Speed and the build quality are less important, but you do need a perfect AF, dual card slot and high MP then the D800 might be excellent value for money.
This is the position I am in now..... I have the money to spend on the 1D X, but don't need its speed, robustness, though I like the ISO capabilities.
However I also know that Nikons D7000 does a very good job up to ISO 3200.
I hardly ever go over ISO 3200, so that would satisfy me.
If I make the switch now, I know I can spend up to 6500 euro's, plus I have some extra glass to sell off, for which I can buy new lenses.
The D800 plus the 24-70 / 2.8 and the 70-200 / 2.8 will cost me about the same as a 1D X. That would give me a start after the switch has been made. Then I can sell of my old Canon lenses and buy some back that I really need, like eg. the 85mm.
This is probably the way I will be doing it if I will jump ship.... but first lets wait for the 5D3 announcement.