There is little doubt that a high resolution body requires more care in focusing and higher shutter speeds. folks use to using a D700 may be in for a re-adjustment period, just as those that were among the first to use the 7D.
However, that is more of a user learning issue and the capabilities of the camera for someone who has learned to use it will be a fantastic upgrade for situations where more detail is needed.
I'm looking for extreme low ligh sensitivity, so my first choice is the 5D MK III, due to the price. If it does not provide, I'll look at the 1D X.
I do think that those who buy the D800 and learn how to deal with the high resolution will love it.