We flew Air transat to Barcelona last month. We did have to connect in Montreal. We had no problems at the airport in Toronto but because of the connection we were at the airport earlier than a direct flight. (I believe it was around 3pm). We managed to get a very good price on club class going out so had a very comfy outgoing flight. On return we had a 2 together seat with lots of leg room and that was fine for a daytime flight. Because we passed through immigration in Montreal we had no issues with long lines but our flight was delayed half an hour because of holdups in Toronto
enjoy Barcelona. We have been often. This was our second trip to Spain in 5 months.