I took "Oslo" technologies for a ride using October 2008 CTP and created my own model schema (using "M" schema), textual language (using "M" grammar) and a rudimentary visual extension in a modeling tool (using "Quadrant" extensibility).  I used a simplified version of UML Use Case domain as an example.  Read more at the link below.

http://blogs.msdn.com/modeldriven/archive/2008/11/23/oslo-example-end-to-end-using-use-case-model.aspx