I had my wedding reception there this past August and it is a very beautiful venue - Great Hall and courtyard.
However there are some problems, No Air Conditioning. They provide large industrial fans but those were not enough. There were 140 of us and definately very warm... Also, we had a curtain back drop for the head table and when the fans were pointed towards us, the curtains didn't stay down. Another thing is they are huge and unsightly in photos. A bunch of our cutting cake photos were not "perfect" because there is a huge fan right behind us... July is pretty bad too I heard a couple had to move the dance floor outside (unplanned ahead of time) because the great hall was too hot. The fans are loud too, we had to turn off the stage one during speeches because we could not hear the speaker. The thing you have to remember during cooler times (September) school is on, there are a lot of students around and it is quite busy around. Hart house is a Student life building primarily...
Also if you do book with them make sure you keep them on the ball - our coordinator was horrible (Devon). She promised us things that were not followed through on, minor things from tealights on the tables to major things like late night dessert table (we pre-paid for it too) and it was not served at the wedding!
It is a very nice venue though... another thing is they have purple lighting -we didn't even know it was there until the wedding reception, not good if your wedding colours don't go with the purple. It would have been nice for them to tell us before the wedding and not having us find out after our walk in during Our Grand entrance.