The live view & video is a nice plus, but the best thing about the D90 is the excellent picture quality at high ISO settings.

I did controlled tests using my 55-200mm VR lens at 55mm (f/4) and looked at ISO sharpness and color on the D40 and D90.

200 ISO is the D90's lowest normal sensitivity setting, and 3200 ISO the highest, although it can shoot as low as100 ISO and as high as 6400 in extended ISO mode.

In an effort to appeal to a wide audience, the D90 features an extensive selection of in-camera retouching options, including D-lighting, red-eye correction, cropping rotating and re-sizing, filter effects, colour balance, multi-image composites and Raw processing options, among others.

I later switched to the 18-105mm lens and put on a Nikon SB-600 flash (I ultimately decided to get a new flash to go with the D90 rather than try to use one of my old flashes) to take the post-ceremony photos (at ISO 200) of my son with family and friends.

Most of these features are enhanced for the D90, especially the CMOS censor (instead of CCD), color depth, movie mode, battery life, higher res screen, controls, high ISO performance and censor dust removal (to name a few).

So if you are really pondering which one to get, I say for most purposes the D90 is a year newer, has video, the same picture quality and low light capability (except for the AF of the D300, which focuses a bit faster in lowlight).

Obviously the 300 is a slightly more professional camera with a better frame, faster shutter, better autofocus, etc., but the D90 is so close to it and comes with a slightly better sensor and is $500 cheaper.

I have learned more about how to alter the depth of focus, the crispness of live action, and to use out of focus backgrounds to complement what is in the foreground - all by playing with the Nikon D90's aperture settings, shutter speeds and the like.

So I take the second D90 with me to work, charge the battery, put a lens on, and I went to a dark room and took about 10-15 underexposed shots.

For example, I was at the 2009 Westminster Dog Show last night, and I took some shots with the D90 and the 18-200 Nikon lens using only the light in Madison Square Garden (no flash).

Ok, so onto the most important thing; picture quality, outstanding is the only word that can be said, the colors are natural and vibrant in normal use, but with the vast array of tweaks that the D90 has, it can make any shooting condition look good.

At the end of the day, pretty much in line with what I expected, D90 excells in specialized usages I mentioned above, but GH1 will continue to serve as general purpose/travel kit thanks to it portability, articulated display, video capabilities and reasonable stills quality.

The video quality is great on the D90, but the focus is a HUGE problem.

video is pretty poor, unless you are doing studio or very controlled shoots, and you REALLY know what you are doing (I have seen some amazing videos using certain lenses with the D90 video, but for the casual videographer, I think you will get much MUCH worse results).