Just saw Cloverfield today, and I must disagree with Pox. I personally thought the movie was great, certainly not the high water mark of cinema but easily one of the better movies I've seen in quite a while.
Looking at his comments, I find it kinda funny that the things he didn't like were the things that I felt made the movie more then just another monster flick. What he describes as "padding" I thought were vital for the atmosphere they were going for, it gave it an authentic "caught in the middle" feel to things. To each their own I guess.
If you are going to see it: wait until the end of the credits and listen closely.