I just finished going through The Marble Nest, took me a bit over 2 hours. The devs weren't exaggerating when they said it was not optimized very well. Ran like a hog on my PC and was stuttering all the time, but thankfully I never crashed or ran into game breaking bugs. As for the game itself, it was very compelling and faithful to the feeling of the original game. The atmosphere was fantastic, comparable to STALKER. I also really liked the music which definitely added to the tension in some spots.
I think I failed some of the events so I might be replaying to see if I can do everything perfectly. There is also a choice at the end which gives you one of two endings I think so I'll check that out too. I did almost die which would have sucked since there is no saving. Everyone in the town is so damn weird it took me a bit to get into the swing of things, but once I did the story got rather interesting. Looking forward to seeing the final product come out.