My husband and I took a wonderful trip on the California Zephyr from Boston to Emeryville, CA (near San Francisco) this past April. We started out with a "roomette" which was not much bigger than a closet, and a shared bathroom down the way. We found the Amtrak crew to be cheerful, helpful, eager to please, and the facilities were clean and not too shabby. The other passengers were fun- the whole experience was relaxed and laid-back, not at all like airplane travel. The food was no worse than most American mid-level restaurants. There was a viewing car where the seats faced out, and you could see the amazing scenery of this great land of ours.
When we got to Denver, the cars emptied out, since they had been occupied by a tour group of Brits taking a "Railways of America" tour. We then upgraded (at a very reasonable price) to a "deluxe" sleeper cabin with our very own tiny bathroom (hint: you sat down to take a shower!).
Best of all, when we pulled into Grand Junction station, there was katlaughing and Roger to greet us!

Downside: the tracks are owned by the freight companies, and they can slow you down for hours. But you aren't taking the train to get there in a hurry, and the laid-back atmosphere was contagious. During one long delay we got out our instruments and started to play (we had enough room in the bigger cabin). We got a small audience who really appreciated it!

I would recommend for anyone to try a long-distance train ride in the US. We hope to take the train to Chicago for a wedding next May. We may never fly again (except to go overseas, and even then we're looking into cargo ships!).

Feel free to PM me, mcpiper, if you have any other questions.
I just told my husband about this thread. He just said, "Well if you can't have fun doing that, you can't have fun!"