When I was a kid a common trope* in sci-fi novels I read was "the generation starship gone awry". So I think I was predisposed to like Pandorum, and given that it dealt with the topic non-idiotically, I was well satisfied. There's not really a lot of intricacy to the plot, but there's a boat-load of atmosphere and the whole ship just kind of feels right, and then there's certainly plenty of mutant-punching-and-kicking-and-stabbing.
FuzzyCo grade: A
* Or maybe there were just a few that really stuck with me.