I was impressed with it. It didn't totally rely on jump scares, which surprised me. I mean, yeah, there were a few, but the most effective fear is a pervasive one and it really does happen through-out the game - if not in you, the player, then definitely in the character you're playing. It's realistic in the sense that he might start breathing deeply with suspenseful nervousness even when an aggressive-looking inmate brandishing a weapon turns out to not have any interest in pursuing you whatsoever.
And that's the thing, when cautiously wending your way through the place you won't really know which enemies are actually hostile toward you until they attack. They're also perfectly happy to chase you while running very, very fast and if you manage to escape into a dark room and hide in a locker or under a bed, you're still not safe - they can and will open lockers or look under beds to search for you, including ones you are hiding in/under.
I won't spoil it for you, but I will say it's definitely worth a play-through.