I have been shooting with Canon digitals for 6 years now (EOS-1D, 1DmkII, 1Ds and 5D, which I use 95% ot the time) and just asked the boss to get me couple of Nikon D700 bodies next. Why? Because D700 is faster than 5DmkII, has better sensetivity, better LCD screen, intervalometer for stop motion video, built in flash, dust cleaner, 51 focus points.
I was also waiting for 5DmkII before my desicion, but I do not see much improvement. I am not impressed with 21MPix sensor, because there are no lenses which can resolve well enough for that. Already when 5D originally came out a major photograpy site made a real life comparason to 1DsMkII at 16 MPix and concluded that 5D at 12 MPix was just as sharp as 1DsMkII at 16 MPix. Tha fact is that it is impossible to get midformat sharpnes with 35mm format lenses, even diffraction starts to show if you close the aperture to smaller than f11. It is not the number of pixels in the file, but what information there actually is which matters.
5DmkII is a major letdown. 5D has been my favourite camera for 3 years, but yes, they are new kids in the block now, from old families.
Maybe I should not write this here, as I am not "Canon folk", but I am not "Nikon folk" either, neither "Minolta folk" or "Olympus folk" even though I have used all those professionally for 30 years. We should not attach ourselves too much to a certain brand but get the best there is at the moment.
I do understand the lens problem, more or less have to stick to one brand, but I am lucky enough to be able to replace everything every now and then. That said, I have been happily working with Canons for 6 years, and the new Canon models are not certainly getting worse, but others are again in the race, and seem to be leading it at the moment.