Pro shooters have been asking Canon for an image-stabilized, wide-angle, general-purpose zoom with a constant aperture, weather resistance, and full-frame coverage. (Amateurs have a comparable one in Canon's $420 28-135mm f/3.5-5.6 IS lens.)
This $1,250 (street) lens, a study in contrasts, is the response. Optically challenged but highly functional, heavy but not fast, a "macro" lens but with average magnifying power, and popular but expensive-it's like the bumble bee, which aeronautically shouldn't fly, yet does.