There are few people I would trust with a story about the end of the world--Steve Carell's everyman performance here looks hilarious and vulnerable. I'm not sold on Knightly but I'll give her the benefit of the doubt.
Few films are born with the stamp, "Future cult classic." Fewer still have the pedigree of filmmaker Timur Bekmambetov, the Russian director of Wanted and Nightwatch, films that are visually brilliant and completely devoid of attention to story.
I expect this to be on the level of Snakes on a Plane for silly fun.