I had a D700 before it was stolen, and after using a FF digital I'm never going back. That said, my flatmate has a D7000 and it is one of the nicest cameras I've used.
RE: AF in liveview - don't do it. It's the first camera ever to use it and it's sketchy at best. You're much better off manual focusing.
Noise wise it has the best high ISO of any crop camera on the market and far better than a certain FF digital too. Shoot raw and process it with LR3 and your files will be virtually noise free.
All Nikons made after the D300 have a different image processing engine, which would explain why you're seeing a difference between that and your D200 (in my opinions it bests the previous one by a mile - I used to have a D70/80 too).
Numbers on charts are all well and good, but you can't argue with that 2 stop dynamic range increase:
Also, I'm not sure if it's just me, but the D7k has the nicest sounding shutter I've ever heard.