Saw it tonight. Wow, I really liked it. Wasn't expecting much, but I think it really delivered. The handi-cam shooting is pretty cool too, I didn't have a problem with the motion sickness but some did. The PG-13 is completely irrelevant, it's not really a 'horror' movie, more fast pace scary, think War of the Worlds. There's still some gore/body flinching going on too.
I would really recommend seeing it in the theaters, just like Children of Men was great in theaters, but only pretty good at home, I think Cloverfield will play the same way.