I can't speak for haml, but sass is certainly a welcome tool in dealing with CSS, since it mostly uses CSS syntax, with sensible nesting to keep things orderly.

I can't speak for haml, but sass is certainly a welcome tool in dealing with CSS, since it mostly uses CSS syntax, with sensible nesting to keep things orderly. sass takes what you already know and kicks it up one notch (perhaps two, if you want to use variables).