How to evaluate if a door is hung correctly?
Plumb, level, square.
On plane (not necessarily with respect to the wall, which may be twisted or otherwise distorted).
Uniform, appropriate gaps. 
Solid attachment, especially at the hinges and strike plate.
Smooth, quiet operation with no gravity-induced movement.
Proper weather sealing, where appropriate.


Experience claim: Hundreds (thousands?) of interior and exterior doors installed or refurbished over 30 years.