A seasonal train service from Bariloche to Las Grutas, Rio Negro has started and I for one would love to try this, as I imagine the scenery will be spectacular.
From Bariloche you leave at 18.00 and arrive at Las Grutas at 0740 with one-way prices at around AR$1470, which isn't too bad at all.
No mention is made of the facilities on board, but a quick look at the frankly awful 90s style website here, gives a lot more information. Apparently the service runs from October to March.
Edit
There's a disco and cinema on board and you get cabins for sleeping.
https://www.google.com.ar/maps/dir/Las+Grutas,+Río+Negro/San+Carlos+de+Bariloche,+Río+Negro/@-40.4761583,-69.3758002,8z/am=t/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x95fa332ef10b0b27:0x82c47ba662165cdf!2m2!1d-65.0943303!2d-40.8108283!1m5!1m1!1s0x961a7b1520c860e5:0x8210ae97cb7b9a65!2m2!1d-71.3102778!2d-41.1334722!3e0
They now have new trains.