Quick comments, no spoilers. but a comment on the "cool thing" at the end.

Rating: 10/10 (21 January 2008)

I've seen a fair amount of comments that this is "Blair Witch meets Godzilla", a rather shallow comparison made by people who haven't seen the movie.
The only similarity, in my opinion, is that both lack a sound track and that both are told from the PoV of those experiencing the events through a hand held camera. ( Note - if TBWP made you motion sick, take something before seeing this ).
Oddly enough, the most recent recent movie this reminded me of was The Forty Year Old Virgin - none of the characters in Cloverfield fell into the horror movie cliché camp, no 'annoying jerk white guy', no 'dumb bimbo who gets it for having sex', the characters come across as people we all know. Likable people. And I think that's Cloverfield's key to it's horror. I didn't particularly care for any of the characters in TBWP, but I did care about the ones in Cloverfield.
I'd heartily advise seeing this on as big a screen as possible.
IMO, it's truly a return to the roots of the Kaiju movies, the original Gojira/Godzilla was meant to be horrific, not a fun fest of a guy in rubber suit stomping models, and Cloverfield returns to that root. Well done Mr. Abrams, well done.
*SPOILERISH BIT* As for the "cool thing" at the end of the credits, I'd advise Googling it, and saving yourself the run time of the credits.