We lucked out and had no wait when we visited - just walked right in and to a table. By the time we left, though, it was packed! I'm not sure if/when there is ever a good time to visit to avoid a crowd, but you might get lucky.
I had the breakfast sandwich on a sesame bagel and it was delicious. We also tried some other bagels and I have to say, all were tasty.
I am someone who loves bread products, and while I'm not sure it was the best bagel I have ever had, it was a bit different in flavor and nice and soft on the inside with a bit of a perfectly hard outside. I would definitely eat these bagels often if I lived in Montreal.
Worth a stop if you're in the area and definitely try to get in to take in the experience - hustle and bustle and quick, efficient (and friendly) service.