I loved it. Even the inevitably cheesy final act couldn't get me to walk away less than entertained. The older you are (to a point) the better it will be as the film's setting at the end of the 70's is done as perfectly as I imagine it could be. The main characters are interesting, three-dimensional (most of them), and immediately help draw you in. Despite the tense atmosphere of the plot, the generous portion of humor throughout spurred more than a few laughs from the audience and, more impressively, never felt forced or shoe-horned into the script. Special effects are top notch and I found that the action was done well enough to distract from the implausibility of certain events.
I won't say anything about the plot. The trailers have all been teasers and after seeing the movie myself, I can understand why. The less you know, the better. Do yourself a favor and give it a go. I can't imagine you'll be too disappointed.