We recently used Skyway Park when flying out of Pearson for a vacation. We'd be gone for 8 days and needed an affordable and secure place to keep the car when we where gone.
It was super easy and convenient! You can complete the reservation online, give them your departure and arrival times and done. They have a little shuttle that will pick you up right at your car in their parking lot (super convenient when you are wearing sandals and summer clothes so you don't roast when you get off the plane in the tropics, but it just decided to finally snow the night of your departure) and take you to your terminal for check-in. Same deal coming back. We gave them a call once we were through customs and they were right there when we got outside. No waiting! I was amazed.
Bonus points for the shuttle guy who gave us a boost when our battery had died over the week we were gone!