Many people used to complain about the acoustics but I really don't have any kind of ear for that. They've renovated Roy Thomson in the last decade, adding in more natural wood.
Pro:
The circular design to the hall seems to be able to accommodate more patrons closer to the stage, versus a rectangular hall. I like there are several balcony seats around the stage. And they're the cheap seats. Maybe it sucks for the acoustics but I love hovering over the musicians, seeing their sheet music, and being able to watch the conductor.
Many drink stations, adequate places to sit and sip your coffee before the concert. Coffee has free refills.
Con:
A serious lack of bathrooms. The only washroom facilities are near the main entrance. When the concert lets out this creates a HUGE log jam of people. People are waiting for their wife/husband in front of the exits while others are trying to get out.
The seating is enormously uncomfortable. You try sitting in those seats for 80 minutes listening to a ponderous Bruckner piece.