Does an event loop really keep the CPU use down in Flash? In C/C++ I've always found that the event polling overhead means that it's ever so slightly less efficient than a game loop, but not so much so that it matters. I thought it was purely a matter of taste?
When Flash isn't rendering to the screen (i.e. via constant blitting), it hardly consumes any CPU at all. In my experience, blitting the screen 30fps causes a lot of CPU load even when you aren't doing anything.