I used the D7000 with an AF-S Nikkor 28-70 lens today to videograph our church service. I used a tripod, AF-F and face priority. The first part went very well. I could watch the little square track the nearest face without having to move the camera.
Then latter on, the Pastor started getting really animated. He walked back and forth and toward and away. This was handled very well until he also started waving his arms around. The lens AF motor started making noise and the camera could no longer lock on. Perhaps the motion was too much? Or, was it the low/bad light? The Auto ISO was at the max 6400. The 1280x720 picture quality was very good.
I used a stereo boom mic because the Tascam created too much noise. You cannot turn of the in camera amp.