I worked on a fairly large project a while back where we modeled the classes in Enterprise Architect and generated the (partial) POCO classes (complete with model-driven business rule validations), persistence (NHibernate mapping file) and DDL. Based on certain model attributes we could flag alternate generation strategies or indicate that a particular portion would be entirely hand-coded.
There was a good deal of initial investment, but it paid large dividends over the lifetime of a 15 developer, 3 year project.
I'm investigating doing something similar with the current Microsoft technology stack. The place I'm stuck is that class modeling is done with the VS 2010 UML tools, but logical data modeling is done with Entity Data Modeler.
Is it a reasonable path to use VS 2010 UML as the "single source of truth" and code generate the edmx files based on the class model? That's the inverse of the common path to create the entity model and use a POCO generator to generate classes. However, a good class model can be used to generate much more than just the properties so I tend to view it as a better choice than the entity model.
Entity Data Modeler is limited to a single diagram per model and becomes unusable in non-trivial scenarios. You can use UML profiles to extend class models for logical data modeling. It requires a significant investment of effort and time which may be justified on a 3-year 15-developer project.