My wife and I saw Cloverfield last night. If you want to see a thoroughly engrossing, exhausting, and just plain fun movie, this is it. We really loved it!
The "live action" feel of the movie using the Blair Witch video-cam technique really made the film work for me. I don't think it would have been near as good a movie without that, just because we've all seen tons of scary movies with plots like this one. But with the first-person perspective, it was a real nail-biter. The acting was great, the special effects were great, the gradual disclosure of the crisis facing Manhattan was great.
And the ending was great, too! I won't say any more than that about that.
Besides the above, I loved how Rob, the main male character, illustrated the love of Christ, who doesn't cease to pursue his wayward, helpless Bride.