Since I found out Box2D, I'm using it for kind of any game-like application I try to write, from very small prototypes or small programs to test something, to actual projects.
Thanks to it it's so terribly easy to handle anything from collisions, to the actual physics.
Sometimes, though, I have some doubts about it: if I only have to handle circles or AABB, and don't need advanced physics tools (joints or stuff like that), I think that a physics engine could add a sort of big, unneeded overhead.
To reassume my question: would you use Box2D (or other physics engines) in a game where physics is really simple (like Super Mario, let's say)? And, if not, why?