Can't say if these are the 'best in Montreal' as I have only a single sample, but they are very good bagels. The bagels are on the small side compared to what is often found in the US/NYC - not a bad thing.
The place is very small, seating is tight for about 20 people total. Expect a line.
Tried the sesame and poppy seed bagels with lox. Note that the salmon(lox) that they serve is very light - almost no salt - so it is different than most lox available in the US (and very different from belly lox, if you can find it, which is characteristically very salty).
The bagel sandwiches were a bit pricey($12) but the bagels themselves are cheap($7.50/doz)
Be aware - Cash only!