I read the online part of the D300 review and the increased AF points are considered a beneficial upgrade. I do wish that we could get real world example of just where one could expect to see the benefit. Clearly someone somewhere needs it and as it's usually a feature of higher end cameras.

In what situation would one benefit from 40+ focus points against 5?

If there are obvious and valid reasons then it should be easy to answer. If it's difficult to answer then one would question whether it's a benefit at all.