+1 on getting there early. 6.15am should see minimal rush but you don't want to risk it. When the line is long it is VERY long. I'd get there by 4.45am at the latest. You'll probably get there and breeze through. But this way you're safe. Grab a Timmy's (Tim Hortons) once through security and relax...better than being stressed by waiting in the immigration line and maybe missing your flight.