Obviously it's very self contained, but those environments look so realistic. I'd be too busy staring at stuff to get scared (well, not really, i'm a scaredy cat, but they sure do look nice).
Anyway, while i thought the demo looked overall great, I do think they should drop the voice. Part of what made P.T. so scary was that there was so little in the way of direct context, making you feel very personally involved. A degree of context can do wonders (such as how the little girl screaming creates a non-forced incentive to rush back into the nope-nope-nope house), but the voice doesn't really add anything that's worth putting an extra layer between the player and the person they're controlling (at least not in this demo).
Even with the voice though, this really does look great. They've done an excellent joke of replicating P.T.'s vibe, and i look forward to doing everything in my power to never play it :p