created a nice little 2D raycasting collision detection library in AS3 which should work with whatever project you have since it uses its own system. Bit of a pain to port vertices from whatever you have to this system, but meh. Price I pay for being "general" I suppose.
Anyway, detecting and reporting every possible pixel-level collision along a line going from (0, 0) to (800, 600) with a circle and a square (poly) takes 7.9896 ms on my PC.
Detecting and reporting the closest pixel-level collision to the starting point (0, 0) with the same data takes 1.2174 ms or 1.4898 ms depending on which object comes first (circle or poly) on my PC.
All-in-all, I think that's pretty alright for most projects. A square is a pretty simple shape, so I'm sure adding more vertices will increase the time it takes, but I'm not sure by how much.
I still have no idea what I'm going to do with this.. Thing- once I'm done with it. For now it's just a big collection of things I developed over time that have been useful to me regardless of the project, engine, framework, or library(ies).
Anyway, back to work. I still have quad tree and pixel-perfect (bitmapdata alpha) collision classes to create.