I spent about 5 days in the place with 7 members of my family. There was ample room for all of us. We especially enjoyed having dinner on the deck one evening.
The upper floor is air conditioned but that does not help those on the lower floor deal with the heat.
Kitchen had everything required to put on a dinner including sufficient plates, cutlery, glasses, chairs, etc.
One word of warning is that if you have difficulty with stairs then this is not the place for you.
Communications between us and the owner were ok. Would have preferred a little more contact but in the end there was enough to make the arrangement work.
All in all, if I had a large group of people I would not hesitate using the facility again. Of course, Montreal is great no matter how big or small the group of travellers.