It's hard to find good vegetarian places - and I travel a lot! Le Commensal was pretty good - but not amazing.
First it's not a sit down restaurant, it's a buffet where you're charged on the weight of the food you pick. You enter by climbing 2 flights of stairs (apparently there is an elevator but it needs a key and someone to operate it). Once upstairs you enter the buffet area and pick from tons of different vegetarian options from several different cuisines. Each item tells you if it include dairy as well as other ingredients.
The food was okay - it wasn't super warm and who knows how long it had been sitting out - but I didn't each anything I didn't finish :)
The location is neat because you get to people watch those on McGill avenue below you while you eat.
Overall, I'm glad we went, but I probably could have gotten something better for the price elsewhere.