The trailer seems to have some updated shots with clearer visuals, there is also a Muto in the Las Vegas scene.

While from all accounts it wasn't a trailer but footage (I wasn't there so I can't say definitely), the crowd certainly seems to be in awe over it. More info as we get it, below is some of what Gareth Edwards said via Zap2It.

Update: The reveal was footage of the Hawaii scenes some of what we have seen in glimpses in the trailers but there is also a reveal of Muto that we haven't and the beginning of a showdown between Godzilla and Muto. Check out the video below.

"We did think about looping the [trailer] footage for two hours," Edwards jokes of the well-received trailer for his movie. Don't worry -- there is still other footage. In it, we actually meet the monster: "Godzilla tells you who he is," says Edwards. 

(Original post had trailer which was removed per Warner Bros.)

The first and third are almost the same, the middle one is one of the few body shots of Muto. Posted in Toho Kaiju Union onFacebook by Jeremy Williams.
Update: Clearer shot of Muto.