Chatime's drinks are good! Some of my favorites include the coconut milk tea, strawberry milk tea, mango juice, and coconut smoothie-- all of course with 100% sugar and tapioca "bubbles". My only qualm is that Chatime is very expensive; there is no reason why a small smoothie with tapioca should cost $6!
I've been to two other Chatimes in Montreal, the one in Chinatown and the Concordia area, and honestly this location is not as good as the others. As others have mentioned in their reviews, the drinks at the other stores have a better taste and quality. One plus about this location however, is that it is significantly larger than the others and serves as a great place to meet up with friends to catch up, study, etc. The front desk even has board games they let customers use-- just don't forget to ask!