Don't get me wrong, its looks like a really nice camera with a lot of advances.But for a camera with that price tag ($3299) It’s looks odd that there are some important features(at list to me) that aren't there but they are in my 'entry level' camera that cost 1/4 of the D5.
I am glad you understand this, lots of people want the newer camera only because it is the new kid on the block, and usually those people don't pay attention to what they need. If the features that are important to you are in an entry level camera, you should by all means get that!
To me, the most important features are the autofocus, build quality or ergonomics (I do a lot of topside too), image quality (color) and resolution, in this order. My personal opinion is that the D2x is better than the 5D in all (don't know about image quality yet) of those features except for resolution (but that's only in paper, I don't know how much of a difference you would see between 12.4 and 12.8 megapixels). Since they have very similar resolution, I think the difference between the D2x and 5D is equivalent to the difference between the film Nikons F5 and F90 (both have the same res. film), so, even with the price difference I would still get the D2x if I was buying today. Now, if Nikon didn't have the 10.5 fisheye I would think twice about the Canon.