Did you have the 18-200 or the D7000 serviced for back-focus issues? I never had many problems early on with my D7000 while I was shooting track meets, etc. Then when I started shooting butterflies, humming birds, insects at a closer range, I noticed "soft focus" issues. The 18-200 wasn't as bad as my new 18-300.
If I need the camera serviced, I'm close to my warranty expiration. Any suggestions?