Models and Oslo
Oslo was the most interesting technology I've seen at the PDC by far, and the Quadrant session was really amazing. If you did not see it yet, go and watch it. They had Quadrant run in the Microsoft Surface in the Expo area, and being able to explore a model using Surface is very powerful.
However, I think several Oslo demo were confusing, in the sense that they used the textual DSLs to define things like 'Music' and create a SQL model for it.
With examples like that, it could look that 'M' is designed to let you define a domain model for your LOB application. And that's not the case. You will use the Entity Data Model for that, and there will be an M-Grammar for defining the EDM, or at least that's what Tim Mallalieu suggested in his presentation about the future of the Entity Framework.
The M->SQL mapping will be useful when you have an application that needs metadata to run. If you have a 'Products' entity in your application domain model, you'll probably have a 'Products' table in your application's DB schema and a set of records in your 'Oslo' DB Schema that describe the entity.