There's been a buzz about this restaurant for years but I've never been until today. I really liked it! It definitely has that cool "Plateau" vibe. Like everybody says, the place is really small and really buzzing (do take out if you are a group of more than 4). We had the chef special, which was about a selection of best sushis/dishes. The food was fresh, inventive and delicious.
Montreal doesn't have a great selection of Japanese restaurants compared to other places I've been. However, Tri is probably one of the best in the city.