I just saw this recently as well. Before I start getting all negative, I will say that it was a good time at the theater. It's a well made film that shows care, polish, and a bit of intelligence.
High points for having the characters realize that they should leave the house and then leaving the house. Also nice they way that leaving the house worked into them continuing the curse, even if that was telegraphed way early
But, as fun as it was to watch and as nice as it was to hear all the kids in the theater scream and jump, etc., the film really lacked creativity and overall was fairly superficial. The design and performance of the ghosts was less than inspired. And Mr. Boogie really seemed like a reject from a black metal band. It almost seemed like they were trying to give the goth crowd a new costume idea for next Halloween. The central premise is interesting, but it really could have been fleshed out into some larger sort of picture. I think the best horror films delve into some sort of larger social/psychological fear and examine and exploit that. This film doesn't really do that and suffers a bit for it.
In the end though, it's a really good disposable Halloween fright ride. But. it's not something that you will remember for long and I doubt that anyone would want to watch it multiple times. But, the craft that went into making the film shows and makes it a very enjoyable run for the time invested.
The sound design is excellent even if it is a bit ham-fisted
Since many are comparing it to Insidious, I'd say that Sinister is not as good as the first half of Insidious, but it's a lot better than the last half of Insidious.