Saw the movie earlier tonight at a theater with one of those pseudo-IMAX screens - huge, but not as huge as at a genuine IMAX theater.
The first thing I have to say is that the sound levels were off the charts in this IMAX format! Damn, I might go so far as to recommend seeing it in IMAX for the sound alone. There were parts of the movie that were literally deafening, most obviously the trainwreck. The girl character also screamed a few times and her screams were practically decimating! I've
never heard audio with this sort of dynamic range at a movie theater - it was totally awesome and added to the movie.
The 2nd thing I have to say is that the music instantly reminded me of Lost (the TV series). No offense to the Lost composer (I know he's the one who did the score) but IMO he could've been more original.
That said, this was a really all-around great movie. It did feel like an 80s throwback back to a time of childhood innocence (primarily from the kids playing around and biking in the streets) and a strong focus on the family element, and more focus in general on the human characters than the monster. So it didn't really feel like a "monster" movie, it felt more like an adventure/drama movie with a monster in it, and even then, there wasn't really that much of the monster.
Not that it took away from anything - the movie was filled with tension and suspense along with old-fashioned character moments, like kids just talking.
I can't really pin down any one thing that made the movie great, it was overall just a really fun/scary/dramatic type of movie that felt odd coming out this decade.

The pacing overall felt very methodical - not fast, but not slow either. And the acting by all the kid actors was really good too - no complaints there. No cases of annoying kids talking too much or chewing comedy scenery - just kids straight-up being kids with realistic portrayals.
The movie didn't even feel like a "summer blockbuster" type of movie, it was that much of a throwback. Sure there was a monster and explosions, and other sub-plots involving the military, but they were shoved to the background enough that they were almost afterthoughts. Kind of a similar vibe that ET had, actually. So not an actionfest, for those who might be expecting that.
Really good movie though. It's the human characters that make this movie for sure - mostly from the lead boy character ("Joe"). IMO this movie will probably appeal most to those who still have that inner kid in them or have that sense of imagination.