getting into component dev in flash, so I just wanted to jot some notes down:

1. mx.core.View is better to extend from if your component has children it needs to lay out.
2. When you are extending from mx.core.View, calls to myComponent.size() are handled by the doLayout() method resize the border_mc (which is the RectBorder for the component that is set up in View) and then call the doLayout() method, which you overrisde in your class. Also, you don’t need the init() method, though (i think) you can still use it.
3. The Flash Help documentation, though it seems to be pretty well improved over mx04, still needs some work.

more to come, im sure.