Laggy SWFs

It ranges from 50 to 60 on my end. The engine spends 10ms on updates, which suggests there's something wrong in the updates of your behavior(s).

Is the "ground" made of actors (~60)? If so, be sure to disable collisions between them.

Being able to disable Box2D for use in games that don't need physics is something we're considering for the future, but to adequately support that, we'd probably need to re-implement some collision detection (which we sorta stripped out of Flixel because we were using Box2D).