"Does combining the media queries have any actual performance improvements? Are people simply raising issue because they don't like the way the output CSS looks? That's a damn good question and one that Aaron also raised. As he put it, "Let's ask science!""
Refactoring Trulia's UI with SASS, OOCSS, and handlebars. My slides from jsconf 2013. Lot's of yummy details about the performance improvements we were able to make. By Nicole Sullivan