The Nikon D90 was a big surprise by featuring 720p HD video as the first DSLR. But Panasonic (GH1) and Canon (5D Mark II, 7D) followed with 1080p HD video.
When we reviewed the D300 (not the D300s) we liked this camera a lot and found it one of the best APS-C sensor DSLRs in the market (counting features and quality). The D300s inherited this strength as a still camera and added 720p HD video.
Here is a short test video:
We still don't know where some of the jerking in pans come from (we use a good head). This shows on all cameras we used and it is not related just to the D300s. I could be also playback or our panning technique. We should use fewer wide pans anyway.
If you want to get the best colors you need to experiment with the JPEG settings in the camera (Picture Style). We did not have the time to find the best settings (this is a quite complex issue). You can make the settings so that it is best direct out of of the camera (need different settings for sunny and overcaste) or best with more latitude for post processing (here you want low contrast, low sharpening and low saturation). We normally aim for a compromise.
You can shoot good videos with the D300s but there are some limitations:
Only 720p at 24fps (this can create some more moire than 1080p, see in the video)
No full manual control like the GH1, 5D Mark II and 7D
Motion JPEG provides more compression than the competition
We have seen very good footage from the D300s which shows that a skilled videographer (we are not quite there yet :-)) can get good work from this camera.
In the end it it very much depends what you want from this camera. If still photography is your main goal and you want to get started with video the D300s is a good value. For movie makers the D300s may not be the first choice.
Nikon started this trend of Combo Cams (cameras that can do both video and stills) with the D90. Now we hope Nikon follows through with future models and supports also 1080p.