The default tree-style Ecore model editor provided by Eclipse IDE is boring. At least during Helios release, there is another, sexier option which is Ecore Tools (Incubation project). I think it's bundled with the "Eclipse IDE Modeling Edition" download but in any case, you can always install it into your Eclipse IDE or an Eclipse RCP Application by using the Eclipse Update Manager:
- Go to Help > Install New Software...
- Choose Work With > Helios - http://download.eclipse.org/releases/helios
- Search for: Ecore Tools SDK (Incubation)
- Right click an .ecore file in Project Explorer view, and and choose Initialize Ecore Diagram File... from the context menu.
- Open the .ecorediag file