I've done a few trips. When everything is on time it's a great experience IMO. When it's running late it can suck. A few things I tell interested people:

Have a different mindset compared to flying. A plane trip is hectic and cramped but it's over in a few hours, it's a means to getting somewhere. Your vacation begins when you land. On a train the voyage is part of the vacation. It's chill and you'll meet nice people.

Amtrak has a website where you can see where the trains are at in real time. It'll tell you if they are on time or how late they are running. This is real nice because you can put off going to the station if they are hours late. The first time I rode they didn't have this yet and we felt trapped.

I got the small room (Roomette I think?) twice. It's small but so am I. It's two seats facing one another that fold down into a one person bed. Another bed folds down overhead. I got my parents a full size room for their 50th anniversary. It was nice but they spent their awake hours entirely in the observation car.

In my experience their wifi sucks but may have improved. Download books and movies in advance.

Bring your own drinks and snacks! Two meals a day were included with the rooms.

When I took the Coast Starlight I watched a YouTube video in advance that gave good advice about when and where to sit in the observation car for seeing Mount Shasta.

Safe travels!