This was one expertly crafted piece of horror entertainment.
The movie's biggest (and frankly only) flaw is that the plot is largely built on the ludicrous idea that a family would ever bring a baby into this world. It's almost impossible to suspend your disbelief about that plot point, but outside of how conveniently silent the baby is, you really can't argue against the movie's execution.
There's a constant air of suspense and the use of sound (in particular the lack of it) really adds to the sense of dread. I did wonder how well mainstream audiences can handle all this silence but then again I couldn't care less since I saw this at a respectable venue with a respectfully silent crowd.
Also
@FlyRy I actually liked the "Jurassic Park" moments as you would call them. One, because they worked and two, because they worked. And when something works you should just shut the fukk up about it and appreciate it.