This airport is one of the largest in Canada and is a huge international hub and it's very cold and unwelcoming at first glance. In the domestic side of Terminal 1 the choices of shopping and eating while waiting for flights is extremely limited (Oh, you don't like Tim Hortons? Well how about some Tim Hortons?) It is slightly better in the US and International flight areas but there are still not very many options.
One of my biggest pet peeves is the "Priority" line at security - it is so non-specific! Priority for who? Passengers with airline status, passengers who need wheelchairs, people with tight connections, as well as aircrew all head to this line. The security screening is pretty standard but US customs hall lineups can be ridiculous. I signed up for the NEXUS traveler program so that I don't have to deal with the long waits in the customs hall, but then I get tossed into the "Priority" mess at security....
I always feel bad for new visitors arriving Toronto that walk around in circles looking for where the public transit stops - the signage is so small and nonspecific. The TTC finally installed token vending machines in Terminal 1 that accept credit cards - but you can only buy 1 token at a time for $3 a piece. It's about time, since most visitors don't know a thing about Toronto transit.
Oh - I was sitting in Terminal 1 a couple days ago in the lounge area near gate 144 and saw one of the girls at the shop kiosks jumping and screaming... and the saw the mouse scuttle across towards Starbucks, towards other passengers sitting and waiting and then disappear.