The biggest advantages of the camera are the wonderful usability, robustness, fast autofocus and the excellent large and bright viewfinder.
The disadvantages are the slightly larger weight and the not entirely convincing noise performance in low light conditions. Since the D7100 and D5100 even with their newer sensors are definitely a bit better.
Also interesting is that your price will remain stable, while the price of the D7100 easy almost monthly decreases.
Since many serious photographers want to have the latest technology and now always go to the D7100 or D610, the D300 is currently very well used to acquire. Who buys a well-preserved for 400-500 EUR, can not go wrong. And also purchased new, it is a sensible decision - at least if they had both cameras in hand. It is no accident you ranked on in Nikon product pyramid and not under the D7100.
Small supplement:
Now, after about two months with the camera, I can say only one thing: The usability is a dream. Whether in winter with gloves or in the city at night; with a flick of your finger is all essential parameters can be set and change. I never have to go to menu. She's always ready to go and thanks to the good and fast autofocus, as well as the continuous shooting mode also excellent for action shots (Children on the slide, boxing matches, etc. allowed). This is what distinguishes a professional camera of a good consumer camera. And then the shutter sound ... glorious.