If you are headed to Montreal, the good news is that it is an extremely vegetarian and somewhat vegan friendly city. Our first meal was at La Paryse -- mostly a burgers and fries place with a very good tofu burger (ask for it without mayo if you are a vegan). Matt is a huge veggie burger fan so he enjoyed this restaurant quite a bit.
The next day we got lunch at Commensal -- a vegetarian buffet style restaurant. I like this idea in theory. My trouble with veg eateries is that I always want to try a bite of everything but I can't eat everything on the menu myself. The problem with Commensal was the execution. All of the food was similar in taste and consistency. The sort of edible and not bad but nothing to write home about fare you'd expect at the home of a friend who's been vegetarian for about 6 months and just learned to cook with curry powder or something. The buffet consisted of salad, soup, chili, curries, baked tofu, etc. It is nice that the place is there and die hard vegetarians might even sort of like it but I wouldn't go out of my way to eat there again. It was the kind of food I'd be happy to find at a rest stop on a road trip if that gives you some idea.
We got dinner at ChuChai, a vegan Thai restaurant. The food was outstanding. The menu was extensive and we liked everything we ordered. We got fresh rolls which were light and cool and refreshing. We got two spicy entrees, mine was "chicken" with basil and eggplant. Matt had something with mock duck. The entrees were the perfect degree of spicy and satisfying without making us feel overly stuffed. Although this was a pricey eatery, the food was definitely worth it.
We got drinks at Jello Bar. This bar was obscenely expensive ($10/drink!) but by far the most enjoyable that we found. They had a really good DJ and the drinks were excellent. If you are going to try just one we really loved their "Key West" martini which consisted of melon liquer, vodka and lime juice. All of the drinks were pretty tasty and buzz inducing though. This bar also had the friendliest bartender (even bartenders in Montreal were not all that friendly).
We also ate at a restaurant called Aux Vivres twice. The service left a lot to be desired. We waited over an hour for our meal and they rarely filled our glasses of water. The food was pretty good though and the entire restaurant was vegan. They had a very good smoothie that had celery in it and a decent selection of sandwiches including a coconut BLT. You can get any sandwich on Chapati bread which is fresh made at the restaurant. I think this works for some sandwiches more than others.
The chili was pretty good but I wasn't crazy about the sweet potato fries since they were kind of soggy. Matt didn't seem to mind though.
If you eat here skip dessert! The truffles were too rich to be enjoyable and the cheesecake was very tofu'ish. Overall the desserts were extremely vegan tasting (this is not a good thing), clearly they need a copy of Vegan Cupcakes Take Over the World.
We went to another bar that was decent called Else's. They have vegan food and Hoegaarden (my favorite beer). They also had some indie rock CDs in rotation which we always appreciate.
We also checked out Le Cagibi, a cozy cafe with tasty coffee/tea drinks and vegan/vegetarian food and Le Divan Orange, a rock bar with vegan/vegetarian food.
One thing Montreal does have going for it is that you can get food and coffee (with soy milk even) 24 hours a day. There are many places to choose from and even vegetarian food is available at all hours. We really liked Sara on the corner of Mont Royal and St Laurant. This 24 hour Lebanaese fast food joint had all the standard Lebanese fare in a ready-in-a-jiffy format. The food was inexpensive, the staff was friendly and the potatoes were really outstanding -- salty and soft on the inside and slightly crisp at the edges. For under $10 we got a plate of grape leaves, potatoes, hummus, bread, grilled eggplant and and falafel.