a) For a bizarre reason, Canon chose to swap around the focus ring and the zoom ring, so you sometimes chose the wrong one. It's not a biggie, but worth knowing
Indeed. The reason might be a design necessity (for example, the lens has a floating focus element), but may also have been by choice. From their market position paper on the lens, Canon is aiming it primarily at APS-C users, and even though the zoom and focus ring placement is reversed from other L-series lenses, it is the same as the high-end EF-S lenses (17-55mm, 15-85mm, 10-22mm).
Cool - never realised that for EF-S lenses Neuroanatomist - definitely a mild confusion with the other lenses I use.