I got mine last december, upgraded from the d200, simply or the liveview feature, i got sick of taking tens of test shots for focus.
I have only had 2 astro sessions with it and the results are very impressive, the d300's noise reduction is fanatstic and you dont even get alot of noise not using dark frame subtrction.
Colour rendition is also a step up from the d200.
But the best feature has to be liveview, while in liveview you can zoom right in on lets say the octans in orion and fine tune your focus in a matter of seconds, then just lock the focuser and you are done.
As for terrestial photography, it is definitely way better than the d200. Its colours are just unbelievable especially whe you crank up "vivid", he colours just pop out. Its 8 fps is also impressive especially for sports photography.
I now its not the full format like the d3, but even the pros sya that the only difference between the 2 is the full format feature, at the moment I canot justify and extra $4K for this feature.
I am waiting to give the d300 its full workout once my observatory is built, then its everything will be up for grabs.
