Visited Beaubien Bagel on a family trip to Montreal a couple months ago. This bagel shop came highly recommended by our Airbnb host, so we gave it a shot.
First of all, the bagels were fantastic--slightly sweet with a great balance of chewy and fluffy. We knew this was a small shop and didn't mind waiting a few minutes for our food, especially since there were 5 of us.
However, the woman working the counter was incredibly rude to not only me, but also my very polite parents. We did nothing to provoke this behavior, except to try to place our order as a party of 5 instead of one at a time (who knew this was the rule? I didn't). This place was our first stop in Montreal and set a pretty sour tone for the rest of our trip.
There are plenty of other good bagel shops in the area--I wouldn't recommend this one.