Not as hacky as using float:left; and overflow:auto; to place block elements in a row. I'd say it is below par.

How is it readable? It's a well understood convention, sure, but the semantics are completely incorrect. The example in the linked article, by contrast, does exactly what it says. The syntax might be a little odd, but the logic is hardly complicated.

For certain connotations of "hacky", sure. But I don't think it's hacky in the sense of being unreliable.

Would probably be very simple to turn it into a clean SASS/LESS mixin. Performance I'm less sure about.