I'll second all the comments so far. The difference between the cameras is dramatic, and dynamic range is a huge part of that.
With the D7000, I am "saving" shots that would have been either hopelessly blown out or hopelessly under-exposed with the D70. You will be stunned at how much detail is waiting in the white/black areas of your photographs.
As for the higher MP count, what that means to me is that I can make some crazy deep crops to pull good images out of otherwise mundane photos and still preserve enough detail for reasonable size prints. I routinely made 16"x20" prints with my D70, and they look fine. But the limitation is you need to be printing more or less the entire original image. With the D7000, even with heavy cropping, I'm making stunning looking 16"x20" prints.