I would highly recommend watching this, and keeping in mind how such a thing could be useful in games.

http://worrydream.com/#!/InventingOnPrinciple

For a concrete example of usefulness in games, see

http://www.youtube.com/watch?v=-32SFFbaeJg

It would be useful to give a pitch as to why I should watch it - it's an hour long.

Because it's an awesome lecture and well worth a good hour of your life. Trust us on this one, but it's your loss if you don't. :)

If it helps, you can read the comments from when it was posted and got 221 points:

http://news.ycombinator.com/item?id=3591298

It's really one of the best ways you can spend an hour imho.

What would you want to use it for in a production environment? (and why is JS source transformation not viable there?)