Pretty much every person who recommended poutine to us told us to hit up La Banquise. It's definitely a popular place. We were there for Osheaga and saw a lot of festival people stopping in their for a dose of Montreal poutine!
The wait time is super long because this place is so popular. We didn't wait for a table but took our food to the park to eat instead. The staff are busy busy busy too. They all looked like they were working hard, which was nice to see. It did take us a while to order at the till though because they were all so busy. We waiting a while to get someones attention, but finally got it. My girlfriend ordered a regular poutine and I tried the mexican one with banana peppers for something a little different. I believe it was called the "just for laughs" or something.
These are huge poutines and they are heavy. You're definitely getting your money's worth here. They were really good too! I'm not really a poutine expert though so I don't have much to compare them to! They were yummy though! I would totally go here again and can see why people love it so much!
I also wanted to say that this restaurant is located next to the most beautiful La Fontaine Park. I would totally recommend going and sitting outside at the park to enjoy your poutine. It's just lovely.