We actually really enjoyed this film... Right up to the last minute, when it's completely ruined by an absurd "happy" ending.
It's cool folks, world killing asteroid releases nuclear winter, but in less time that it takes to gestate a baby, everything will be fine.
I can disconnect from reality long enough to believe that people had 48 hours notice before the world ends, even that you can drive from Kentucky to Canada in six hours while every road in America is full of panicked people and flaming death, but the ending was so painfully unrealistic all you can do is laugh at it.