Convenient, clean, fast and affordable. I used my Presto card to pay for it and it is only $9.
It is a nice, and fast ride. It was quite easy to find it at Pearson. There are signs everywhere and there is an information table at the arrivals level. You can also purchase tickets in terminal or just before boarding the train. I believe you can even purchase tickets onboard the train (at least the announcer said so).
You can see the train are new, the ride is smooth and the interior is clean. The only reason why I don't give 5 stars is because the hours of operation. Last time I arrived from Denver, the train was already closed. They should be operating as long as they are planes arriving at the airport.