all right well here is my opinion. I dont have any canon experience, but i love my d200. I was concerned i would regret spending so much money on a camera, but that is not the case. I am so happy with it. the lenses that i am shooting with are the nikkor 12-24, which is plenty wide enough imo, and the Nikkor 18-200 vr. Both are fantastic. The vr works flawlessly. When i am shooting ski photography, I usually just take out the 18-200, which covers mostly everything that i want to shoot. If you are not ready to spend 900 dollars on a lens I would reccomend the 18-70. Incredibly sharp for the price. Its a great lens to start your lens quiver with.
For those saying the D80 and D200 are pretty much the same except for a couple different features, that is not the case. If you have both, side by side, the D200 is a much more substantial camera. It is metal, not plastic. If you have felt the F100 and N80, that is pretty much the comparison. The N80 feels like a toy and the F100 feels like a pro camera. For the extreme conditions i shoot in, I feel the D200 is necessary to stand up to the elements, but that is just my opinion.
Get whatever you are more comfortable shooting, in regards to Nikon and Canon. I grew up shooting Nikons, so it was natural for me to buy a Nikon, especially since I have access to a bunch of Nikon f-mount lenses. But if i didnt have this background, I could have just as easily convinced myself to buy a Canon.
I hope this helps you out. If you have any more specific questions, let me know. And if you want to see some of the shots i have taken in the last few months of learning the D200, on my flickr page, let me know.
Also, a big fuck you to whoever is so narrow minded to say get a Canon or get a Nikon. They both make fantastic products, that are equal. However, I do not think you were comparing the right Canon with the D200. I think the 20d is the one built to compete with the Nikon. But correct me if I am wrong.