I had previously planned to be on a plane from SFO to YYZ today. However, my company cut travel way back and I had to make some choices. At least I got a short visit into Toronto a few months ago as part of another business trip.
After 9-11, I got a little paranoid and chose to fly back from Europe through Toronto, instead of directly back from Paris to SFO. My sheer speculation was that the terrorists would leave Canada alone for awhile! What I actually got was a tight connection and a LONG walk from International to US Customs.
The airport itself is big and clean and of course (like other Canadian airports), the luggage carts are free. And the Air Canada part of Pearson is the place to be.