It depends on which line you take. Amtrak has different service levels on different routes. When I took the coast starlight from Seattle to San Jose it was wonderful, with clean cars, great food, and courteous service. When I took the southwest chief from LA to the middle of the country, it was a completely different experience. The porters were still friendly but the equipment was grungy and frequently broken and the food was about what you’d get at Denny’s. Bear in mind that both times I was in a ridiculously expensive first class cabin.

I’ve never taken the empire builder, which runs east-west across the northern part of the country, but I’ve read that it’s a “premier” service, so it should be on par with the coast starlight.

Edit: c/grey food/great food/