Booked one way tickets from Montreal to Quebec City. The website was easy to navigate, however, it didn't like the one credit card I was using and though my company said it was good to go, it just wouldn't go through. That being said, everything was great. Now granted, I recommend spending the extra money and ride in the business class. With your ticket, you get to sit in the air conditioned lounge, in nice comfy chairs, while you wait for your train to be called.
A porter comes to announce your train and escorts you to a separate line to board the train first. Once in, your assigned seat is roomy and comfortable. A beverage service comes through, and then lunch is included. There's also a coffee service after. There is also a separate lounge car you can hang out in as well. The attendants are readily available as well!
This was a fun way to see some of the Canadian countryside. I highly recommend traveling in business class if you can. It is so worth it!