Next week Nikon should release a new firmware for the Nikon D90 according to this email I received today:
"Nothing crazy. Some interface improvements. Apparently an ISO tweak. There's nothing that can be done
about the Jello Video thing... It's a hardware problem, that will probably be there even in the next couple of
generations of SLR w/ video models. But there will be a slight improvement in the d-movie compression. It seems that the compression on the blue channel is too high, thus causing the stair-stepping. And there will be a compression rate selector deep in the menus. and......as far as I know, that's it."