The only free Wifi spots I've had luck with (not including coffee shops) is the Apple Store and Druxy's (downstairs, South end). You can sit in the food court from as far as the escalators.
This mall is pretty much the flagship of all the stores in Toronto. Even the Victoria's Secret angels opened the new shop.
Hectic like a madman on weekends but great vibe for locals and tourists. Even current renovations have been carefully crafted to make still look aesthetically pleasing.