I don't think you have anything to worry about, as long as you don't set your expectations too high. Amtrak provides generally good service, but it is seldom perfect. Superliner coaches can seat about 70 people, and while they can be popular, they are never packed beyond capacity. Even when full they offer much more personal space than you'll ever get on a bus or airplane. You get gobs of legroom. I can put my legs straight out without hitting the seat in front of me. Seats are also wider than bus or airplane seats. You can recline them without putting your headrest in somebody's face behind you, plus you get a leg rest and foot rest. If you get tired of sitting you can walk around the train (except into sleeping cars) at your leisure.
In the summer the cars are air conditioned, in winter they are heated. Sometimes the air conditioning works a little too well.
The Superliner rest rooms are my personal pet peeve, but they are not bad enough to discourage me from traveling. The regular rest rooms are very tiny, and the sink faucets have a tendency to splatter, but Superliner coaches also have one spacious handicapped rest room, which you can use, even if you are not handicapped. If you can handle airliner rest rooms, you can handle rest rooms on the train.
Food in the dining car is good, and often excellent depending on who is cooking on your train. If you don't like it, tell your server and they should offer you an alternative. Food in the lounge cafe is limited to pre-packaged and microwaveable stuff, which may or may not be to our liking.
And the scenery between Salt Lake and Winter Park is some of the most spectacular scenery in the country, especially east of Glenwood Springs. And the only way to see much of it is by train.
Don't worry. Enjoy your trip.
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Trust God, love your neighbor, and never mistake opinion for truth.
-Mr. Toy
The Del Monte Club Car