I won't use Sass, Haml, LessCSS or things like that until I see Sass, Haml and LessCSS in Firebug or View Source (or whatever your choice of web development tools).  The claimed benefits are nice in theory, but I think it is a debugging roadblock to have to mentally translate and associate your source code with what the web server serves.<p>If I code in CSS and HTML, that problem is practically nonexistent (excepting things like templating).  The CSS and HTML the web server serves <i>are</i> the CSS and HTML in the source code.