Re: Incredible quality
Low levels of illumination in a scene will certainly show noise more than higher levels across all ISOs. It's down to bits per pixel decreasing with each stop of underexposure. Which is why it's important to try to expose properly. To my eye there really isn't anything special about that ISO200 shot. I've just looked at a few of my raw files also shot at native ISO 200 (I do a lot of night shots) and there really is no difference noise wise - as it should be. I don't do any noise reduction on camera, I save that all for post.
The real balls of a sensor shows when the ISO gets higher, and although those ISO 3200 and 6400 shots are good, they don't look as good as the article lead me to expect. I remember the D3S's shots being more impressive.
Now I've got to go find some good side by side ones to compare!