In the last 2 years: 16 airports, 50 personal arrivals/departures, 7 friends pick-up/drop-offs = alotta headaches! mostly airline related though.
Having said that, most of my positive experiences have been at Pearson.
Positives:
a. It's clean, ultra shiny
b. There's a "cell lot" (FREE parking while you wait to pick up someone)
c. Shuttle from Viscount station (cheap[er] parking lot) runs between T1 & T3 often and quickly
d. Many snack options
e. International flights leave from here! (Do you know how frustrating it is to live near an airport that goes to 2 places?)
f. Lots of signage makes it easy to navigate.
g. Large washrooms. (Try lugging a large suitcase/backpack into a tiny washroom and you'll know why this is important.)
Negatives:
a. No efficient public transportation to the city core, yet. Supposedly slated for some time soon, but Pearson is the only airport I've been to in a major city that doesn't have transportation down yet. Get on it!!!