I flew Airtransat twice to Canada, found them great.I don't like Air Canada. I was last there at a conference in 2008 and we stayed in the university accomodation in downtown Toronto. Found it cheapish, basic, but very central, and great breakfasts! I can't recall the name of the place, but it was right beside Eglington square. They were renovating it, so it might well be re-opened now. There are some hotels down on the waterfront, near "front" street. This is very central as well, near business & entertainment districts. Personally tho, I would prefer somewhere nearer the University/Eglington square area. It's a bit quieter. The centre of Toronto is very walkable too, and the transport system is good. If your thinking about going to Montreal, check out flights with Air Transat too or alternatives too. The train journey is both long and expensive.