I have the D300s but so far I did not explored the video capabilities of the camera.
Looking on the web to see if there are any good samples I have found this video.
The filming is of excellent level with heaps of awesome action and photos extracted from the film to appreciate the quality.
I think that the D90 can perform as good as the D300 and the D3 will be awesome.

[nomedia="http://www.youtube.com/watch?v=2E9ElqZOlaw"]YouTube- Nikon D300S Adventure Sports - Robert Bosch[/nomedia]