hitTest vs Walkable

ok well I sort of understand the concept of using walkable tiles or platforms as opposed to hitTest… but not really. Since I’m not using tiles ATM, Tonypa’s excellent Tile tutes don’t really help in my situation. I’m basically look for an alternative to using hitTest on platforms mostly to save on CPU power and to make things faster. is there a way to do this in an art-based game? anyone have examples?