With as few spoilers as possible: It had some good effects and good moments (one bit was a true standout to me) but some silly moments, predictability and bad dialogue. Would not say it's the worst sci-fi film I've seen, I liked it much more than something similar like Cloverfield, but it's not great. It's worst failing is that it seems derivative of many other sci-fi movies, including possible spoilers Cloverfield, The Matrix, District 9, Independence Day, Aliens etc.