Since there are no roads to Aguas Calientes and we didn’t want to hike 4 days on the Inca Trail (OK, Dan did want to hike a day or two but you can’t decide this at the last minute since there are so few tickets permitted and besides it is an all or none proposition…no hiking part way).
The train to Aguas Calientes wasn’t completely full but the return train was. On the train out, there had been a problem with our meals not being vegetarian/gluten free (easiest way to order for Dan’s preferences). The conductor/manager/whatever his title was remembered the date/time of our return trip and he presented us with a small bottle of Pisco and a shot glass. Pisco is an alcoholic drink from Peru and Chile and is used in many mixed drinks. It was nice of him to remember us.
The ride itself is scenic and we chatted a lot with our seatmates on the way out. They were from Switzerland but they were actually from some other countries.
It takes just under 2 hours one way for the ride on these modern comfortable trains. 
There are two companies who provide this service, Inca Rail and Peru Rail. We rode both trains during our stay in Peru.