Finally watched this over the weekend.
Overall, I just couldn't get into it. The effects were really well done. And I sort of liked the way it twisted and nodded towards the original. The "cold turkey" aspect was very clever, and did a good job of keeping them in the cabin. I will bet that it would have been a lot more fun to see in a theater where I could have at least had the benefit of hearing the audience reactions.
But, I felt the characters were distant and hard to get involved with. Acting was mediocre most of the time, with the main male lead being pretty bad. I really thought that they could have used a bit more humor. Not necessarily in a slapstick (Evil Dead 2) sort of way, but just that showing a lighter side of the characters themselves would have gone a long way to getting me to care about them a bit more. I get that the whole situation for them all was heavy from the beginning, but a bit of levity or playfulness in their early interactions would have really helped me care for them as characters. As it is, they all came off as detached fodder for the effects.
The score was terrible. Just terrible. I really think they should have gone with something more avant-garde and aggressive, like they did with the trailer. I can't stress how much this pulled me out of the film other than to just say "terrible" a bunch more times. Terrible terrible terrible...
In the end, I found the whole thing to be fairly unnecessary. They may have improved on the original in terms of effects, but they also lost a lot of the other strengths that the original had going for it. Mainly, they lost a lot of the originality.