$19 to get to or from the airport with the presto card! Great deal!!
Walking from the TTC over to the UP Express train is a pain though. It's not the distance (it's relatively short), but it's soooo confusing. The signs are poor, the arrows point weirdly. Have to go upstairs or downstairs and such at some point. I'd have to say that even after doing this about ten times now, I still walk the wrong way and have to back track. This isn't a fault of the UP Express, just really poor signage at Union (but what else is new, eh?)
The train itself is pretty quick: ~30 minutes to get to the airport on it (35 to be exact). It's clean. I hope more people use it. And I hope the price drops even more (but that's just wishful thinking). Even at this price, it's still a great deal!!