J'adore Montreal! We went in to check out the Notre Dame Basilica while we were in Montreal last May and it was so beautiful! I can't believe we didn't burst into flames when we walked in the door! I am from Vancouver, so this was unlike anything I had ever seen in my little hometown before. The architecture was amazing and there was so much attention to detail that you could have spent hours in there going over every little pulpit.
We went during the day when it was not so crowded, and took some photos, but we also came back at night for the light and sound show, ($10 to get in) which was really cool too. They did a really good job on lighting the Basilica and using projectors to tell the story of how it came to be. After the light show you were allowed to take photos but it was much more crowded than during the afternoon, so I would recommend to anyone who would like to get some pictures of the Basilica to go during the day when it is slower.
They also have a little store open during the day where you can buy rosaries and crucifixes to exercise the demons at home. There are also confessionals you can go into, but I didn't run into any catholic priests, so I didn't feel the need to confess, however, I am going back again this year in May, so maybe I'll have to work off my penance then ;)