This is a classic 'take your friends to the woods and kill them' first-time horror movie, but it's so much better than other similar movies that it deserves a watch.
First, I want to commend the outstanding lighting. I can't remember a better lighted movie. Every scene is just as dark or as bright as it needs to be, you're never confused about who is where or what is what. If you're a student of lighting or cinematography, especially if you want to make horror, this is a mandatory watch.
The cinematography is also very good throughout, never betraying a budget, as are the effects. The director holds his cast through what must have been a fairly frustrating shoot for some of the actors (you get to wear blood makeup for 3/4's of the movie! We're nowhere near a shower!). This is a professional movie, and I couldn't tell if it was made for 1 million or 10.
The writing is well above par for this type of movie. There is a character who makes decisions that are very frustrating for the viewer and freezes more than you want him to, but that is good writing, not bad as some reviewers have complained. You get a feeling from the script that these people know each other and have relationships deeper than what you see. The plot moves along at a nice clip, and the comedy comes at the right moments to relieve tension and is genuinely funny. The last line works in a special kind of way where it's predictable, you want it said, and yet it brings a smile to your lips when it is said.
One more thing, the gore is pretty normal for the whole movie, but the ending turns to a couple of concepts that definitely pushed me past my comfort zone and made me feel very squeamish. While most of the movie is horror of the jump-scare sort or the tension sort, the last few minutes get to some psychological horror that is genuinely disturbing. It felt scary and squidgy at the time, but it was appropriate and elevated the movie past a basic type of horror movie.
Hokay, so I'm giving this a 10 because it seems horribly low-rated to me. I think the movie did everything it set out to do, is scary, funny, and fun in parts, and feels like a complete piece. It gets a lot of average ratings but it doesn't feel like an average film. I see that a lot of people dislike the ending, but I'm not sure what they wanted/expected. The script went where it wanted to go. The ending ramps up the gore and is all but certain to shock you. Definitely worth a watch for yourself to see if you agree with them or me.