Boy don’t I know this – in a prior life I wrote a GEF editor for a workflow engine.
Let me be blunt: In the past, creating graphical editors within Eclipse using the Graphical Editor Framework (GEF) was slow and painful. It involved understanding a complex framework and quite a bit of redundant code. That said, GEF is an excellent framework for creating graphical editors because it is model-agnostic. On the other hand, being model-agnostic creates its own problems.