I was surprised when I realized how many people don't like this movie because it leaves many question unanswered. Throughout the history of mankind most frightening things were those which couldn't be seen or explained. Expecting evil is usually more scary than meeting it. (That's why the best of Halloween is first part of the first movie). In fact, I was pleasantly surprised that such a movie came from USA, especially from TV, and after watching these reviews I'm even more glad that someone still makes movies for those who don't rank movies according to gallons of ketchup-blood on screen. Of course: Friday the 13th fans should avoid this film.
Recently I saw a Swedish horror "Det okanda", and I suggest it to those who want to check my statements about fear of unexplained. From USA movies I could chose an early Spielberg movie "Something Evil" which didn't become as great hit as his later works, probably because audience didn't get enough explicit horror scenes, and a final answer. Also, most of the monsters (aliens, genetic freaks etc) look rather funny than scary when they appear on screen. If not at once, surely some years later - try to watch giant bugs, or Martians in 50's or even earlier horrors.
Finally, I don't say this is a great movie. Though I like to think during and after watching, and explain things to myself, I still have no idea what is the meaning of the raven, especially in last minute or two. But I do hope that there will be no sequel: some questions should stay unanswered.