It's convenient because of its location.
Not really. It often takes me
longer to take the Porter shuttle bus from Royal York Hotel that has to drive through Toronto traffic to Eireann Quay than it takes me to take UP Express and arrive at Pearson International 25 minutes later. I timed both in the last few months at roughly the same time (3:30 - 4pm window).
My office to the Royal York Porter bus was just over a 5 minute walk.
The bus sat waiting for a while, maybe 10 minutes (not counted). Buses depart every 15 minutes.
It left, got stuck at several red lights, then inched along on King behind a streetcar, then stuck in car traffic from Portland to Bathurst and inched along down Bathurst for 10 minutes. 28 minutes.
Total time: 33 minutes – Bay Street CBD to Billy Bishop (not counting wait)
My office to UP Express station. 6 minutes. 1 minute more than to the shuttle stop.
Waited 6 minutes, sat on the train another 6 minutes (not counted). Trains depart every 15 minutes.
Arrived at Pearson in 25 minutes.
Total time: 31 minutes – Bay Street CBD to Pearson International (not counting wait)
Yes, Billy Bishop is downtown but one has to contend with downtown traffic to get there. UP Express changes the entire calculation. The A-B connection in one train makes YYZ effectively one transfer away from Union Station in the heart of downtown.