Hey Stu, you now have a third option...
Nikon UK - Products - Catalogue - Digital Cameras - SLR - Professional - D300S - Overview
I'm really not that bothered about the HD Movie mode myself and can't understand why this seems to be such a popular feature in DSLRs. To me, stills and video are very different beasts and trying to do both in the same piece of kit means too many compromises.
The thing that interests me the most about this model is:
Quiet shooting mode: perfect for discrete photography, the sound of the camera’s mechanisms are noticeably reduced.
Other than that it's not very different from the current D300. You get one more frame per second in burst mode and an SD card slot as well as the CF slot but that seems to be it.
Dave P.