Time of the Season? That got me on side right away. And it's rare you see a teaser trailer this prepared to sit and wait and build some suspense.
I'd say that was pretty efficient.
From the blurb:
Based on a true story, The Conjuring tells the horrifying tale of how renowned paranormal investigators Ed and Lorraine Warren were called upon to help a family terrorised by a dark presence in a secluded farmhouse. Forced to confront a powerful demonic entity, the Warrens find themselves caught in the most terrifying case of their lives.
I think Wan's films have been getting better the more he makes. I hope this continues the upwards trend.