I was at the Sherway opening and got there around 30 minutes before opening. I was one of the first 300, but I don't think I was too far from the cutoff.
It still took me about an hour to get inside, and at least another hour just to line up and pay at the cashier. I hope they have additional checkout crew for this opening, because they really needed to improve that at the Sherway opening.
I suggest going as early as you possibly can.. if you arrive an hour early, you'll likely save an hour just waiting to get in so it works out the same anyway. If you arrive right at the opening time, you will probably have a 2 hour wait to get inside and by that time the first 300 will be gone for sure.