I watch a lot of horror films, and sadly the quality of the vast majority of them trends toward the low end of the scale. Often, I come across a bigger budget horror flick that has great special effects but is unsatisfyingly thin on plot. Conversely, every once in blue moon I'll stumble upon a lower budget thriller that has a great plot or a unique twist that leaves a lasting impact.
The Conjuring has the best of both. I'm not going to go into specifics or offer any spoilers, but this was one of the better horror movies I've seen in the theater in a long time--possibly dating back to Paranormal Activity 1 and 3 [for some reason, the even movies in that series are awful, while the odd ones are great].
The Conjuring has a unique premise--which is so important in horror movies--fine acting, and high quality effects that produce lots of scares. Even more importantly, the film taps into the Hitchcock-ian quality of using suspense to make the audience squirm in our seats.
Very satisfying watch--if you're looking for a late summer scare, I highly recommend "The Conjuring!"