We have used Enterprise Architect and IBM Software - Rational Rhapsody. We have used the build in code generation engine and our own code generation engine that generate code suitable to Do178B qualification. With Rational Rhapsody we targeted VX Works as well as our own OS. These tools uses UML models. Since it generates code you can do unit testing with what ever you used to tools that provide integration into these tools.
Scade is also a option if you write safety critical software. Some of the other divisions in our company has used this successfully. It is very logic orientated so it is not able to do everything but it can generate up to 70% of the code for some projects. Using a qualified tool eliminates most of the testing. It has an model verification tool and if the model is correct then code is correct. It integrates in requirement and configuration management tools.
For non safety critical development by experienced developers it is difficult to say if using model driven development will provide you with any saving. It is worth trying, as technology matures and more developers get used to model based development, we will see a lot more of this in the embedded environment.