Certainly worth watching. Those that hate this movie would likely love the movie if they knew what they were going to watch. So to save yourself a headache and reading though all the reviews, here's a solid explanation of why it worth watching.
A nuclear missile is heading to the USA from unknown origin. When discovered, its estimated to hit in 19 minutes. This movie gives you the experiences from 3 sides; broken into 3 segments, and what decisions would be made when faced with such horror. Unfortunately there is no real ending, and I imagine that upsets people, but it was interesting to see how things could unfold had something like this happen.