I just notice that a new version (1.01) of Smultron has been released. Smultron is an excellent open source Cocoa based text editor for OS X, that is fast, has basic support for ActionScript color coding, and has a single window document model. You can find a list of changes here.
You can find more information about, as well as download Smultron from here.
Btw, I have my own version running locally which adds support for compiling (Publish and Test Movie) FLAs, which I will try to release in the next couple of days.