I know Machine for Pigs is pretty far in its production right now, but while the experience of Amnesia was indeed full of dread and horror, I think there is one flaw that it overlooked that greatly dumbed down the horror aspect, and that is the disappearance of foes after a while remaining hidden.
I still think Penumbra is superior in the terror department simply because the enemies continued their patrol in an area and you were always looking behind your back to make sure they weren't sneaking up on you. It carried out the tension and kept it going until you completed a stage. I was disappointed that the majority of enemies in Amnesia simply got whisked out of the map entirely when you sat in your safe little corner for a duration of time.
I think Amnesia would benefit a lot more if enemies stayed and patrolled an area. This would help the horror aspect a lot considering stealth would be more difficult and better strategy would be required to survive an encounter. Does anyone agree?