I think the biggest comparison will be with The Blair Witch Project, and I don't think that's unfair, or even particularly negative. BWP succeeded by getting the audience into what the characters are experiencing, much like Cloverfield literally only lets you see through their eyes.
The downside to this is: more shakey-cam. I understand some people don't like this style of filmmaking, and that's OK. I think it's good when used appropriately, and I totally think this is the perfect situation for it.
The characters were actually pretty decent. Bonus points for the use of relative unknowns, too. I totally didn't expect Hud to be our main guy, and I was a big fan. Rob and Beth, well, I could do without, but I expected as much. The people in the rows around us also giggled when they got to Beth's apartment and it turned out she was still alive. This is probably my biggest complaint with the movie. (And I totally knew I recognized Marlena from somewhere.)
And all this on a $30 million budget? Nice. And they managed to keep the monster's appearance secret too.
Being a Lost fan, I kept an eagle-eye out for references or other hints, but didn't see much. Other than the Slusho shirt, yeah. But no commercials for Oceanic Airlines, no suspicious numbers, etc. I wager once it comes out on DVD other fanatics will dredge something else up.
Added plus: no explanation for the monster! It doesn't even get a nickname. I would have been upset if they did try to shoe-horn in a background, actually. That being said, Godzilla really worked because of his place in the fears of the atomic age, and similar can be said of King Kong, Frankenstein, etc. I'm interested in how people will see the Cloverfield beast as a reference, with the movie's focus on the digital camera/YouTube culture and of course terrorism and 9/11, probably the biggest cultural touchstone of our generation.
And it won't be the end of the story, either. Lost broke new ground with its use of tie-in websites, online games, and viral marketing targeted to obsessed fans, and other added content. The imdB FAQ lists related websites, official and otherwise (also, Wikipedia.) CBR checks out the tie-in manga, which really makes me curious as to where this will go next. A second movie would be interesting, but I'd like to see a clever take on it. Can the story simply continue in other venues? Sure, I'm happy with that too. Wikipedia and Google will let me catch up quickly enough with the work those aforementioned obsessed fans will put into tracking things down. It's a new world order out there, people.
In case you didn't stay until the end of the credits, at the end, we hear some static and someone whisper something, which was apparently: "It's still alive."
Bonus: here's an excellent interview with J.J. Abrams about the movie.
Oh, and, apparently sneak previews don't get trailers, so nothing to report there.