We thoroughly enjoyed our train trip excursion. We traveled "first class".
Each passenger is assigned to a car. Each car has an adjoining outdoor car. You're not allowed to travel between adjoining cars; there's a hefty fine if you do. Luckily the weather was wonderful so we could view the sites from our adjoining outdoor car. The outdoor car affords the best 360 degree views. Views from inside the closed car are good, but for me the outdoor views are the best. Each car has a tour guide and a bartender: both of ours were great. From the outdoor car, our tour guide pointed out all the significant sites, shared amusing stories, and mingled with the guests. The indoor car has comfortable seating, a bar, an electronic-narrated tour/music, and a bathroom (which was clean).
I rated my experience 4 stars, instead of 5, because I'm not sure the increased fare for first class is worth the cost. As a first class passenger, we were provided complimentary champagne (very small portion poured in a plastic cup), potato chips, and an assortment of chicken wings, veggies, and fruit. The food was good, but not great. Honestly, I would prefer to bring my own snacks aboard, but I was told you're only allowed to bring your own a water bottle.
You're not allowed to go into other cars, so I can't say what the other accommodations were like compared to ours. However, I do think our car had fewer passengers, but I'm not certain. Other than the food, I don't think there is any difference in terms of quality of service or comfort, and since each car has an adjoining outdoor car, you can certainly avail yourself of the outdoor views from any car on the train.
So, all-in-all, I recommend this trip because it affords you views that are truly breathtaking.