One other thought. Everyone in this thread, including myself, is neglecting the price difference between these two cameras. The 5D is that good that it is compared directly to the 2N for the type of photography you're interested in. That said, when you factor in the price as well, it's an absolute no brainer IMO. With current rebates, you could buy the 5D, a great fast prime like the 35L to compliment your zooms, plus a 580EX for the price on the 1D2N (roughly, I didn't actually do the math but I'm sure it's in the ballpark). Basically, the 4 major things you pay for in the 1D2N are:
Excellent AF -- more for the excellent Servo mode, for static subject in "one shot" mode, there is just not much difference.
Speed -- if you need 8.5fps, there is no absolutely no comparison to 3fps. No amount of image quality or resolution or low noise will substitute for this.
Weather resistance -- For most types of photography, this is really a non-issue.
Ability to customize -- Again, a non-issue for the most part...the customizing of the camera probably won't make or break your images.
Having said all that, the feel of the 1D2N is addicting and I'd hate to be without mine, but the 5D is your camera, no question about it. Just one other thing... please consider weight a non-issue, if the 1D2N turns out to have more appealing features for you, DO NOT let the weight of the camera sway you away from that... just deal with it, it won't cost you any great images.