Customs
Took an 1.5 hours because they put people in separate lines by flight time, they let the early flights go through customs first, so if you arrive early to the airport there no benefit. Also the line is a huge mess because the only have lines for 5 times of departure 10, 10:05... If you're not part of that there is a huge blog of people waiting for those lines.
Also, there was no priority line for customs, why pay extra for upgrades or you you have status when they don't give you any benefits?
Once you reach the US customs, only 1/8 of the customs officers are on duty, this is the bottleneck at 8am on a monday. They waste countless hours of hundreds of passengers everyday because they are understaffed.
Security
Took 10min, they only have air canada priority line. So if you have star alliance gold status, you cant use the line. Pretty useless here
Flight
Delayed 40min due to slow loading of luggage, this part is solely due to the airport.
Overall Pearson airport is not efficient, not on par with the world's leading airports. But it is essentially the only international airport in Toronto.