Where others provide only generators and compilers we also ship interpreters and runtime metamodeling. For instance, you can start using your DSL and your domain specific tooling long before having completed the metamodel and the related behavior.
Furthermore, we support domain specific notations at every phase of the development cycle including unit testing and debugging. Have a taste of a visual debugger session at the domain level and you will never want to fallback to the textual Variables View of a Java IDE.
If you liked the visual exploration of source code in Inventing on Principle, and you tried to guess how much live coding with instant feedback can improve everyday developing experience you should attend the session Integrating model driven technologies in the publishing industry at CodeGeneration 2012.