Yeah Nape looks really, really nice. It's the reason for me to look into haXe. I don't think it will replace Box2D that easily, as it's become somewhat of a standard. Plus, I don't know how much Adobe likes it that people develop with haXe, but I don't really want to go into any technogoly flamewars/fights, as my post was about getting more performance out of Box2D projects. I'll take a look at Nape for future projects.