I live in Mississauga and every time I go to the airport, I use Blue and White Taxi - 905 274 4444. I don't know if they serve Burlington.
Their fare is reasonable (compared to coming back from the airport) but the main reason for using them is their punctuality. Every single time I called them, they are on time.
They are also acommodating when we ask for a van (the 4 of us have travelled before back home with 10 volumes!!!).
Last October, there were 6 of us going to Cuba and they found a car that would take us all at once.
Camil