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.
There's a disco and cinema on board and you get cabins for sleeping.
They now have new trains.