Sorry for the vagueness, this board doesn't exactly bring out the verboseness in me
The example only adds reactions in the StageMediator, but as an exercise you could go ahead and replace all of the event handlers in the other mediators with reactions (make sure they extend FlashMediator or FabricationMediator). The reason I left it this way is because the original HelloFlash example demonstrated using Fabrication in some mediators, and not using it in others, so I thought that I would continue this tradition.
I don't fully understand Darshan's comments about Reactions not working in Flash, maybe he meant that specifically for when you're compiling with Flash CS3 you can't use reactions. As for how I got it to work, I really didn't do anything special. In this example, only the SWC file is compiled in CS3... without any classpath....and without any code... basically just the graphics are compiled in the SWC. The actual SWFs are compiled using the Flex SDK.
Technically you might want to call this a PureAS3 project, but Flash CS3 is used for creating purely graphical elements without any code attached. The actual view components are creating by composing these CS3 elements into a class, as opposed to how it was done before with inheritance. (I actually find this composition method more intuitive vs inheritance method, and the code hinting also makes it a sexy work-flow)
