The storytelling in the movie was amazing. Like most good stories, it focused on the relationships among people. Yes, it was a horror/action movie (and there are some nice action sequences), but that's not what it's really about. I love the fact that monster (and monsterlings) itself is only rarely seen -- and when it does, it's used to heighten the tension among the real characters. Similarly, each action had a purpose, moving the story along. The choices which the characters made (although sometimes eliciting a "don't go in there!!" yell) were exactly what I felt they should do, as characters. They felt scared, hopeless, and ultimately real.
I'm expecting some complaints about the action, the need for dramamine (I agree), and the weird acting, but overall Cloverfield was an excellent story about people thrown into an extreme situation. The action was secondary, and rightly so.