I should add on a semi-related note, I'm actually kind of glad that AC held my checked bag overnight... the bag-drop line at YYZ on Sunday was an absolute gong show (as allluded to in another thread), and I was happy to avoid it at the cost of wearing the same pair of underwear two days in a row.

All things considered AC does a pretty good job with the chaos of these types of IRROPS situations, but man oh man do the lines ever get long quickly at YYZ. And there are few things I hate more than waiting in long lines!