Somewhat unrelated but I had a terrible time with Air Canada a couple weeks ago for a YUL > EWR flight. Flight was canceled right before it took off. Gate agent was like "Sorry. Flight cancelled due to weather, here's a pamphlet with information and this is the exit door to lead you out of the departure area, we can't do anything for you."
That wasn't the issue. The issue was I had purchased liquor at duty free and needed to return it. I very clearly asked the gate agent if going out that door would still leave me the opportunity to return it. "Yes, no problem". Well the door dumps you into the connecting area of YUL, leaving you no way to re-enter the airport without passing through customs back into Canada and then security to go back to your flight again, where you now have to check the bag with liquor in it.
Gigantic pain in the ass. Wasted over two hours of my time from having to check and retrieve the bag. Fortunately, they were able to rebook me manually on the final flight out that day, automatically I would have been stuck 2 days.