As technology improves, the ease to take better and nicer photographs speeds up quickly.
With nikon d300's 3d tracking, 51 point area focusing, its sometimes quite hard to miss a moving object. The success rate is high and it gives you, as the photographer confidence
With a higher success rate, it translates to lesser wastage of unnecessary shutter counts (that is depreciation which is a cost!)
I'm no spokesman for nikon but a camera like this has definitely eased my worries of getting lousy pictures for stock.