If you like horror movies, especially the old haunted house style films of the 1970s, you'll love this film. The director wasn't afraid to linger on the ghosts and the demons, and there aren't any fake-out scares in this film. No cats jumping out of shadows, no birds squawking accompanied by an orchestral sting. When the music and the scene is building up suspense, it's because something is about to genuinely happen. I felt the hairs on the back of my neck pricking up. Beautiful direction, and the lighting was fantastic. It was never so dark that you couldn't tell what was going on, and even when scenes were completely lit, they managed to give them a feeling of claustrophobia that built up the terror.
The acting was brilliant, especially the children who really sold just how terrified they were of what was going on. In particular, there's a scene where one of the girls is staring at a space behind the door. Even though we the viewers couldn't see or here anything, the abject terror on her face and the wonderful lighting freaked me right out. I kept expecting to see something, but the director wouldn't dare give us that satisfaction. When her sister is standing in the shadow, and the girl says "Oh my God, it's right behind you!" I just about peed myself.
Better yet, the movie has a resolved ending instead of leaving us with a pointless cliffhanger. This is a horror film that doesn't need a sequel. It stands alone on it's own merits, and boy howdy does is do an awesome job of that.