Sorry I never came around to reply on this thread after my Peruvian adventure, but better late than never.
After 4 days on the Inca trail, I took the PeruRail Expedition train back to
Ollantaytambo, and a cramped minivan to complete rest of the journey to Cusco since tracks between Ollantaytambo and Cusco are not in good shape so not all trains go to Cusco anymore.
For the 2-ish hours trip from Aguas Calientes to Ollantaytambo, the $78 fare is ridiculously high considering Peru's cost of living if you ask me, although the train is very comfortable. The seats are wide plush leather, attendants serve snacks and drinks at your seat and the windows are large but my entire journey was after dark so I don't know jack squat about what the scenery looks like.
The train station at Aguas Calientes is a madhouse late evenings when multiple PeruRail trains depart, along with a bunch of IncaRail trains too. The waiting area reminds of Penn Station in commute hours, and the train staff are adamantly anal on checking everyone's passports before letting them on the train, delaying the process.