DXOLabs is now publishing a free website--DXOMark--featuring their test results from dozens of camera models. Their tests are confined to the raw sensor data not overall camera features or performance, but if you're curious about an objective measurement of image quality this is a great site.

It's fun not just to compare current models, but also older models to see how much better our cameras are now then a few years ago. They have a very nice tabbed comparison UI that allows you to compare up to three cameras.

From a quick check you can see that the D300 sensor measures with slightly higher noise than the D3 and D700 which measure almost identically. But all of them score higher than the former flagship D2X and of course than the D200.

Enjoy!--David