In terms of surprises, but this is very subjective, I find it quite light compared to an old 28-70 L 2.8.
Also note that the diaphragm is circular to f / 5.6 or so, the bokeh is quite soft and closing more, he finds a hexagonal shape and produces pretty "effects" star on night lights for example.
Small precision in case: Should be mounted on full size (5D, 6D, 1Dx)! It would be a shame to use it on an APS-C sensor, prefer an EF-S 17-55 or equivalent.
