I liked it. See it sooner than later, before someone spoils it for you.
I liked going in keeping myself in the dark as to what it was and what happens. Too bad my wife had to leave after 20 minutes, she got sick from the jerky camera movements.

Though I think the city being torn apart by a monster is more remote than cell phones working in a subway.

Not to spoil anything - but in the last 30 seconds of the film, keep your eyes scanning in the background, it'll explain a few things.