Fisix seems pretty solid, but I dislike that I can’t open up their code and look at it. Their docs aren’t good enough for that to be okay in my opinion, it just slows me down not being able to check out the classes for myself.
Box2d comes highly recommended but the documentation seems poor and largely based around the C++ version, and the code seems overly abstracted and confusing for even simple projects.
APE seems pretty solid.
You guys have any favorites?