Well, according to the dpreview, video is the only difference and certainly it seems to be the only 'important' difference.
I think that there will always be a difference between the low light performance of DX and FX so to slate it for that is hardly shocking. There are enough upsides to DX for DX to sell well. The price of lenses for FX means that I would have to be a busy pro or find a pot of gold to go there.
My interest in a D300 is one of ergonomics and build quality. It seems to be a good camera with all the right buttons nicely to hand and they can be had used for not much more than a D90 (which runs it a close second). I meant what I said about the video so I don't consider that any kind of advantage between D300 & D90.
Maybe I should stop looking and get on with using my D5000 more until I get over the way it doesn't suit me.