I go through YYZ T2 INS just about every week -- usually on a Tuesday morning. Even though the lines are huge it is difficult to see what AC or INS could do better given the limitations of the terminal. And I have yet to miss a flight... Today at 6:45am, for instance, all 18 INS booths we open and the AC staffer with a megaphone strapped around her neck was doing a pretty good job of managing the situation IMHO (certainly a lot better than 6 months ago). In summary it looks like a zoo but appears to work OK....

Personally I get much more wound up on returning to YYZ from the US between 8pm and 9pm going through Canada immigration....