In case you haven’t heard Adobe has released a new compiler for Flash and ActionScript. The new compiler does exactly what the legacy does, and mostly without any changes, but faster and better. Or at least that’s what it is supposed to do, but it’s still in Beta. So far you could only try it with Flash Builder 4.7 but thankfully there is a workaround for flashdevelop.
This post is based from this one by Alama, so in case you know French go on and prefer his guide.