I've been wanting to see proper support of combinations of column-height, column-width and column-span for a long time. I would definitely be a user of a library if it could give me these features.
Looking at http://www.w3.org/TR/css3-multicol/#spanning-columns it seems to me column-span is implemented exactly like the site in question, i.e. wrong from the point of view of existing behaviour (that behaviour being all the printed magazines and newspapers since we worked out how to mix text and images.)