Saw it last night, and first off, let me say that I definitely am prone to that feeling of being SERIOUSLY freaked out by a movie; "Child's Play" (yes, with Chucky
) did it to me back in elementary school, and "The Ring" in high school, for example (and I have no doubt that "Paranormal Activity" would trump them all, so no way in hell will I ever see it). However, I've seen so much sci-fi in my life that really nothing surprises me anymore, so most of the stuff that happened on the alien ship was freaky but familiar ("ah, so the set designers decided to adopt the 'slimy/gooey/organic' alien aesthetic"
), and as far as torture scenes in films goes, I'd say that was definitely on the milder side of the spectrum.
(Semi-spoiler warning)
However, I quite enjoyed it overall, probably because I went in knowing that the focus was on the other guys and their difficulty in trying to convince people their story was true, and was able to get into it (it's amazing how much a movie/game/book/etc. not being what someone expected can negatively affect their opinion on it; I've definitely experienced that more than a few times, though I'm usually able to appreciate the positive qualities experiencing it for the second time, when I know what to expect). I thought it was really well-acted and directed, especially all the scenes related to the alien side of things; that red in the sky really was extremely ominous, and man, the scenes after Travis got back I found incredibly convincing and intense, especially when they first found him, as well as when he was spazzing out under the table, and we see the syrup creeping to the edge until it lands on his face and his eyes just roll back in his head, damn...
(end spoilers)
In short, I'd say the best word to describe the movie is "gripping" (rather than particularly scary, at least IMO)