i've watched the trailer a few more times, and my initial dissappointment has become something slightly more optimistic.
once you get used to the blue people, it does look pretty darn good, and in 3D ought to be spectacular.
it is interesting that promotional stills of the Na'vi being used to promote the trailer, actually make them look slightly more photo-realistic than the moving images of the trailer itself. you can see the skin textures etc