I was on a business trip to Montreal and stopped in here for some bouldering. Problems were fun and varied in style a lot. I found their grading system a little arbitrary; what's wrong with numbers? But grading is inherently arbitrary so who cares.
The gym was crowded when I went (7-9pm on Thursday) but that made it easy to meet other climbers. Everyone I talked to was super friendly, which was great for me as a foreigner in a new city. If I ever end up back in Montreal, I will stop by again.