We took four flights with Air Canada this summer, blogged about here and here.
Three of the four flights were delayed, one delay upon landing, and two of the delays were over one hour.
Seems to be a repeating pattern.
So much so that, when we were running through passport control in Toronto, the US Customs Agent looked at us, stamped our passports and said with great disgust, "...Air Canada has been screwing with customers for over a year now... since the changes, they don't have enough personnel... some day they will make the wrong customer late and there is going to be a huge lawsuit... good luck making your flight home."
Three of four flights delayed. Something to think about if you are booking flights overseas, with connections.