One of the legit "great food" spots in Montreal. Yes you'll likely wait in line and yes it's well worth it. Service is very good and friendly, prices are reasonable and the food tastes great. The atmosphere is also really nice - I believe the small size of the place adds to it and makes it more special.
It's also great to see a Japanese restaurant without the standard sushi fare we see at 99% of the other places! This is real Japanese food, and it's really well done.
For the vegetarians out there: try the Okonomiyaki pancake (ask them to remove the fish flakes that goes on top) and also the veggie hot pot... both are excellent.