Shifra and I went to see Cloverfield tonight. I loved it; she thought it was ok. I'm not going to give away too many spoilers, but if you want to see it with a clean slate, do not continue reading.
In fact, one of the best things about this movie is that I didn't know anything about it at all going in. I purposely avoided all reviews, and did not spend hours searching the web for hints about the monster. Apparently there was this whole storyline on the web about some Japanese company that may have accidentally created or awakened the monster. Well it wasn't mentioned in the movie, so I don't think the backstory is that important.
What I especially liked about this movie was the first person mode, which you'll either love or hate. The entire story is the tape from a video camera that was found in Central Park. Watching the film from the characters' perspective allowed me to feel the anxiety they were feeling as their city was overrun by a giant beast.
The monster itself is actually scarier before we see it. They could have done a much better job making look a lot more fearsome. But wow is it huge and destructive.
9/11 was definitely alluded to in this movie. There's a scene when a large building (I think it was the Empire State Building) is toppled, and we see the debris rushing toward the camera. It's almost right out of news coverage from that day.
Basically this was a very good movie and substantially scarier than I Am Legend. I actually thought it was also a much better movie. Definitely worth the price of admission.