I have finally gotten around to creating a simple demo application that illustrates the majority of GEMVC's features. It is in the demoapp directory off the main trunk. You can create a flex project to build it or if you have ant you can use the included build.xml file (see comments in build file). GEMVC also has its own build.xml file as well.
The Demo uses ColdFusion for the backend remote service and assumes gemvc is checked out into the web root or there is a CF mapping for gemvc. The Demo also illustrates the use a dynamic tree that uses GEMVC services to load each branch upon opening.
GEMVC 1.5 official release is imminent.