I spent some time the last few days recording a short screen cast on M.  You
can view it here:

to M
(~ 39 minutes)

One thing I would say about M is that it may be different things to different people. 
This video is just one example of what you might do with M.

I say in the title that "M is like an Onion" as an homage to Shrek (if you
haven’t seen this movie look here – Ogres
are like Onions. 

It isn’t because M smells, but because M has layers.  There is the whole "M". 
You can split that up into MSchema, MGrammar, and MGraph.  Each part might be
useful.  And any one of them has a number of different interesting scenarios.  

In this scenario my concept was "I’m a .NET developer, I create tables in a database
to hold my application data, so how might I use M?".

Check out my new book on REST.