There's some serious FUD going on here. Not only are valid CSS files also valid Sass files, but CSS files in the app/assets/stylesheets directory are served up

There's some serious FUD going on here. Not only are valid CSS files also valid Sass files, but CSS files in the app/assets/stylesheets directory are served up just fine. There's no need to learn Sass right out of the gate. And Haml isn't even included in the default install, so that's a complete red herring. Finally, JavaScript files in app/assets/javascripts work fine as well; as with Sass, there's no need to learn CoffeeScript right away.