I'll find the direct link for you once I'm at my desk but there is layover ticket you can buy to ride the express into the city. It's a rapid train that goes right into the downtown core of Toronto and there are so many things you could do, the aquarium, the CN Tower, the Waterfront and get a beaver tail ... lots to do other than watch planes land.
I recommend when you check in that you asked for a room that does not face the tracks for the link train unless you're able to sleep better than I am because that darn thing runs about every 5 minutes and it stops in front of the hotel before it carries on and then comes back. You do have to ride that thing though if for no other reason than you can pretend you're on the monorail!