As the second camera in the Nikon range, it rivals the flagship in that it has the same number of pixels, namely 12.1 million. However, the D300 is not a "full frame" (35mm film frame format) camera, as is the D3.
The D300 has rapidly gained acclaim as a sports camera, because of the magnification factor introduced by its smaller sensor and the fact that it performs very well in low light at high ISO, though possibly not as well as the D3.
The D300 was succeeded by the Nikon D300s in 2009. With good image quality up to ISO 800, up to 7 images per second, and max. shutter speed 1/8000 sec. it might be again a good performer for sports photography. It still has just an APS-size 12.3 Megapixel CMOS sensor.
image by Uwe Kulick (Image rights)