The primary drawbacks of the D90, as a video camera, are no XLR outputs and no professional viewfinder. .
There is a much larger issue that need to be addressed: how existing live view nikon's overheat and become unusable after 5 minutes (sometimes taking 15 minutes plus to cool down before being able to take still photos again, let alone turn on live view again. I've yet to see any pratical hint (let alone demonstration of D-movie) that it will hold up to the rigeurs and demands of shooting a short or documentary
that said, i preordered my d90. it fits the bill perfectly for some spontaneous 90 second video clips that would have required rental of a pd170 . and it will serve as interim camera untill i replace my aging d200 with the d700.
viva la revolutione!