Gabriel is also the author of the popular Pipes Haskell library, and nice person in general. Both of these make me heartily recommend his other blog posts about various Haskell topics, which often portray advanced features remarkably well.

Examples:

Scrap your type classes: http://www.haskellforall.com/2012/05/scrap-your-type-classes...

Hello Core: http://www.haskellforall.com/2012/10/hello-core.html

Coding a simple concurrent scheduler yourself: http://www.haskellforall.com/2013/06/from-zero-to-cooperativ...

Tutorial as part of library doc (!): http://hackage.haskell.org/package/pipes-4.1.1/docs/Pipes-Tu...