Hi,
Personally I wouldn't bother unless you really,really need the video feature and the extra 1fps out of the camera without using a battery grip. It's been debated on here before with regards to it's worth, I'm not planning on selling my D300 anytime soon just for the ability to record video that's for sure, but then again in saying that other's may deem it a necessary upgrade.
I'd be more inclined to either get a D700 or wait and see if something else comes along(D400 rumours are aplenty)
Mike.