I've only ever flown from Montreal on connecting flights. The security and customs staff are great. Service was efficient and I was able to get through the necessary work to get to my flight. However, that's where it ends.
The amenities and services are terrible. If you're departing from gate 17-34 there are no amenities except a make shift canteen that sells a couple sandwiches and water. Make sure you grab something before you make the trek to this section. Otherwise, you'll have to back track to the new section. It's also difficult to find a map with a list of amenities. This should be the first thing you see when you enter a new area/section.
After we back tracked, we went to the closest restaurant (Moe's) which only had one item on their large menu. Nothing was in stock. Our next choice (other than a canteen) was Tim's. They too were out of a number of food items and forgot part of our order. They also figured they could substitute stuff without even asking.
Overall, we were not impressed.