Well written, though a tad [ok, way too] long. Having had TJ reject a Coffeescript related pull request of mine on a project of his I have experienced his and the Learnboost teams distaste for Coffeescript.

My problem with CS is the way it is taught and demonstrated, with every example trying to outdo the last in how much syntax they can leave out. It makes the code "pretty" but unnecessarily complicated. Otherwise I am a fan of reduced boilerplate, comprehensions and the like. Just don't expect me to remove () just because I can.