My engine is a 2D full game making solution with AS sitting in it's heart. Basically there is going to be a free license where the engine source is not provided, but a dynamic library can be downloaded. In this version the game makers can use AS to write game code. Basically all engine functionality is delegated to AS and I'm measuring the time spent in the scripting system.
The proof of concept game is now shaping up based on the engine, proving that a full fledged game can be made by using only scripting without touching the engine code. The good news that there is no slowdowns in AS so far, but I'll provide you cases when they are showing up.
I use autohandles on my script interface. The solution itself can be compiled to use native calling conventions or generic, based on the target device (I use generic on android mips and used to use it for arm too before). I use macros like