I am a very frequent traveller and I will tell you here are what makes Toronto Pearson one of the worst airports in the world!
Fees and charges: Pearson has been known to have the highest landing fees in the world and in 2007 they reduced these fees. But of course it was just a facade as what they do is nickel and dime you elsewhere. How about charging $2 for a luggage cart with no refund for returning the cart? Why charge for such a necessary convenience for many? What a cold welcome to tourists traveling to Toronto. First most tourists will not have a toonie on them and secondly at the carousels the porters circle like vultures to "help" people with their bags. Sure for a price. Compare the cost of the porter service with the carts.
More fees? Yes you will notice if you arrange car service your departure from the airport will cost more than your trip to the airport. Why is that? Because they charge limo drivers a fee to pick you up. Instead of your driver meeting you at the terminal or just calling them when you arrive, you go to a booth where the lazy ass attendants barely do their job. It would be great if the fee perhaps resulted in a quick efficient an orderly service but you get nothing for the money. Very often smokers congregate near the waiting area despite the no smoking signs. The useless attendants and security do nothing to enforce the rules. During busy times, often the area is jammed and nobody is directing traffic.
Getting to and from the airport: It is unbelievable that Toronto has no train service to/from it's major airport. Getting to the airport is a horrible experience. If you drive you have to fight traffic and face expensive parking. Take a cab and risk being taken for a ride. Take a limo and you pay a premium for a clean climate controlled ride that is reliable.
The only saving grace is that if you are a premium American Express card holder there are many perks that make things a bit easier. Priority lines, discounts on valet and on site parking and the Amex Lounge helps some of us but not all.