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