You guys are probably privy to this but here's a nice write up from The Man himself on garbage collection in as3.

We're going to start taking care of things here in NY by providing a standard method in (almost) all the swf's we generate that will take care of killing itself (stopping Timers, tweens, etc) and generally cleaning up its p00p. Of course, this will ultimately depend on ass-tight documentation since we all like to play resource musical chairs on projects...