ActionScript 3.0, forget about AS2.0, it's getting obsolete, not to mention it's slow compared to AS3.0.
Most of the "baww AS3 is too hard" complaints stem from users being too stuck with typical AS2.0 newbie mindedness (no type declaration, no OOP, using onClipEvents, etc). If, and only if, you had used AS2.0 properly, moving to AS3.0 would not be problem.
So why even bother with AS2.0 when you can go straight to AS3.0?