Some people tells me I misunderstood the question, but others tell me that its a nice answer, so I will let it stay, eventhough its not providing an answer for an alternative Flash editor - sorry about that
I'm currently moving FROM Flash and Actionscript 3.0 to Unity3D Framework. Its a GAME-ENGINE made for GAMES and there is a free "Indie" license where you get 95% of the engine features for free forever.
You can later on, upgrade your license to PRO (1500$ or something) and then you will be able to use the latest game technologies for bloom-effects, realtime shadows etc.
With Flash I had to develop everything from scratch and spend a lot of time preventing people from decompiling my sourcecode so they could cheat.
Dont take me wrong, I like Flash, but it wasnt made for Game-development, eventhough its possible.
Unity3D has never been made to make "banners" or "movies", but is a pure crossplatform real-time game engine.
You can choose from webplayer (small plugin around 2 mb install) that works on both MacOSX and Windows. Or you can choose installer (real Windows EXE or similar MacOS bin)
and if you buy the license, you can also transfer the games/applications to mobile devices, consoles like Xbox, Playstation and Wii.
So, if you want to make sure that you develop on a gameplatform that also is "allowed" on Steve Jobbs iParanoid system, you should consider switching to Unity3D platform as I currently am.
www.unity3D.com for more info.