Not frequently does a movie happen to provoke me to log in ASAP and post a negative review. In fact, I normally don't post movie reviews at all. But this is one movie that caused a strong response in some regions of my brain.
I normally have no problem with gore and violence, provided there is a point to it. This movie has lots of blood and spilled guts but the point is largely absent.
It appears to be a carbon-copy of some American horror flicks, including the "surprising" (not) plot twist at the end. Except American flicks of this nature are more organic and less pretentious.
Comparing the incomparable, this movie has a similar plot twist to "The Secret Window", except the latter is about 20 million times better and I don't have to use subtitles or suffer through the dubbed dialog. And having experienced awesome French movies before, I expected at least something watchable.
In its defense, the movie has good camera work, sound and is indeed very tense.
I can see how some people might find this movie appealing. Watch at your own risk and only if you have time to waste.