Thanks for making and publishing MPS... it is a pretty incredible program. I've tried to work with several other domain-specific language tools in the past, and it usually ends up that the level of complexity they add negates the benefit you'd hope to get from them... MPS feels very natural and easy to work with. Thanks also for the calculator tutorial at http://www.jetbrains.com/mps/docs/tutorial.html, which was very helpful in getting started.
Keep up the good work... I think you are on to something really good here!