I also own the 18-200 which I use more often. Whenever I can I prefer to get the 70-200 out because it is RAZOR sharp and produces images with the most sublime colours. The AF is incredibly quick on my D200 and rarely hunts. Be aware though, it is long and it is heavy. I pulled it out at my daughter's sportsday and it raised a few eyebrows. This is not a subtle lens - you have been warned.
It costs a bomb but the quality beats the 18-200 hands down. That said the versatility of the 18-200 means it sits on my camera 80% of the time. If you can rob a bank, get one, you won't regret it.
(Written by: DigitalD)