As being an horror aficionado, I was very excited to see Sinister. After seeing it, i my verdict is that it's gt really good stuff in it, but it's got alot of cheesy stuff too.
So Sinister is a good psychological horror movie, directed by Scott Derrickson (The Exorcism of Emily Rose) and stars Ethan Hawke (Before The Devil Knows Your Dead, etc.).
This movie has got great suspense and Hawke pulls off his best performance in years.
Sinister has got great scares, but some of them are lame and cheap, like several "jump scares", where something pops out to the screen, making short, cheap, but effective scares. Although, it's got also some suspense scenes and clever scares, so it's not appropriate for sensible kids.
Overall, Sinister is a very good horror movie, it's got a great story, unlike other horror movies, where the story doesn't advance (this one does) and the mysterious entity Bughuul (a.k.a. Mr. Boogie) is scary as HELL and the diabolical Super 8 foud-footage films of families being murdered in twisted and gruesome ways, like being hanged in a tree or burned inside a car, are very creepy, especially the Lawn Mower scene. If you've seen this movie, you'll know what I mean ;)
Sinister is far superior to Paranormal Activity or Insidious