For a movie about the world ending by massive alien-based slaughter, this movie is laughably bloodless. I guess that comes from the premise: alien balls of electricity take over the world by zapping humans into ashes. No carnage. No gore. Just PG-13 ash murder.
This is not a complaint, though. The movie is fast and enjoyable enough that I really got into the rhythm of run-hide-zap-scream-motivational-speech. The dialogue is pretty dire (one climactic speech outside a submarine is particularly painful), but that never really mattered to me. The best fwiends drama between the two male leads was also half-baked, but thankfully so, because who comes into a movie like this wanting to spend half the run-time watching two guys bicker about a failed business venture!
As I write this, I realize that this does not sound like a ringing endorsement... and it really isnt. This film is bad in a bland, forgettable way. But I will say that, if in the right mindset, you can wring a few moments of enjoyment out of it. But ignore the speeches. God damn those are awful.