Like any right-thinking individual, I have a great deal of affection for the Zombie Apocalypse sub-genre of horror. My favourite zombie film remains George Romero's Dawn of the Dead, aka "the one in the shopping mall." That film has just the right mix of tension, satire, horror and laughs to make it an undead classic.
Zombieland isn't in Dawn of the Dead's league, but it is funny, heartfelt and even romantic. It's sensitive and sincere. The four characters - known initially only by their hometowns - each have their own quirks, and while broadly drawn, they grow and change throughout the course of the film to outgrow their stereotypes: neurotic nebbish, redneck, spunky little girl, slick con woman. Each character has a growth arc, even though they're kept busy killing zombies and scavenging the wasteland throughout the film. The film plays the apocalyptic situations for laughs most of the time, then stuns the viewer by reminding us of the very human cost of the end of civilization. The redneck's obsessive quest for a popular snack food masks the pain he's really feeling, while the nebbish's obsession with his rules of survival clearly shows that his coping mechanisms need to change if he hopes to experience emotional growth. The women, too, are faced with the necessity to make themselves vulnerable, to trust in others in the worst possible circumstances. Yes, this is just a zombie film, but because the characters are more than cardboard cutouts, the audience gets invested in the story. We care about these people, because they're very much like us.
The film makes clever use of special effects to transform credit sequences and pop-up subtitles a living, breathing part of the film, a technique that reminds me of nothing so much as Will Eisner's technique in his famous comic strip, The Spirit. This sort of thing is becoming more common - I've noticed it on Fringe, for example. Some people might find the device intrusive, but it struck me as quite clever.
Horror film sequels have a mixed track record, so I won't call for more adventures in Zombieland - the ending is satisfying enough for this film to stand on its own. But if a sequel does come along, so will I - not for the zombie mayhem, but because I wonder if these characters have more room to grow.