Contrary to popular belief, you can't simply rely on your fancy camera to nail it for you regardless.
No I haven't tried the d7000 for real but I'm a content owner of a 7d. Personally I think the 7d has a great af system particularly for it's price. If you learn properly how to use it is definitely a good system. Do I ever swear at it? Oh yes! Is it faultless? Oh no... Of course not. Would I expect a 1dx af system to be faultless at all times? No.
I have had experience recently with a nikon d90, it's af system isn't on the same plane as the 7d. My partner was having trouble tracking really fast (I mean fast) penguins in the water at our city's aquarium. They couldn't do it, I showed them even with an af system nowhere near the capabilities of my 7d... It can be done. I got some clear of some extremely energetic penguins in the water. Actually clearer than the shots I got with my 7d because there was a cpl filter on the nikon, I don't have one myself.
What am I suggesting? I'm suggesting who cares, yes buy a camera which suits your needs, but before, after and during, skills matter more. Btw, the d300s has a better af than the d7000.