I really liked it. I thought it was an original spin on the tropes of horror films. The story was full of good twists that kept it interesting. The characters were fresh and fun with enough individual personality to make them all interesting.
However, while all the plot twists were good, they were all telegraphed a bit too heavily about 5 minutes before each of them happened, which made it a bit easy to see them coming and sucked out a bit of the surprise for each reveal. This was a shame as the story on a whole was very original and had they left out the "signals" and let the surprises come with less warning, it could have packed a bit more of a punch. It almost felt that while the ideas at the root of the script are really intelligent, it didn't seem to have enough faith in the audience's intelligence or ability to follow the twists without warning.
But, with all that said, it is still a pretty damn good film. People are right to say that it's not very scary. But it is still immensely enjoyable and I'd still recommend it to anyone. It's still clever, fun, and thrilling. It won't give anyone nightmares, but it will certainly give you food for thought about the cliches of horror films and what their implications are.
Maybe it's just because I've been on a "Supernatural" kick, but it reminded me a lot of some of the episodes of that show where the story gets a bit "meta". And, I really enjoyed the movie in the same way that I enjoyed that TV show. I'd also say that the movies overall tone reminds me a bit of "Tremors". So, if you liked that film as much as I did, you'd probably get a similar kick out of "Cabin".