The ambience and feeling of being in the house was great; it was eerie, silent and scary. The darkness felt thick and enveloped the player and the minimal light source only allowed a little bit of surroundings to be shown which was effective in makeing it more spooky.
The mannequin parts were pretty freaky and they did scare me, but it felt out of place as well as there was no foreshadowing of the mannequins as there was to the shadow demon dude. So maybe having a mannequin placed somewhere the player would glimpse at it might have made things more cohesive.
One other suggestion would be to use another way of using the keys as it was a little annoying at the end; the time it takes for shadow-demon-dude to catch up to the player is very little and the player has to stand there and switch keys to then unlock the door which then has to go through the animation before it unlocks. Kind of felt like having a faster way of unlocking the door would be better, but the above stuff did make it more hair raising to escape.
But overall it was a pretty neat and great game! Was tonned of fun to experience and good luck with any other projects you have planned!