As both a Scooby Doo and a zombie film fan, I enjoyed this movie immensely. The movie starts up several years after the gang has broken up, and has stopped cruising around in the Mystery Machine. Fred is the producer of Daphne's TV show, Velma owns a mystery book store, and Shaggy and Scooby are (predictably) total slackers who go from job to job together.
Daphne decides that after years of exposing alleged ghosts to be frauds in masks, she wants to try and find some real ghosts for her TV show. Fred surprises her by getting the gang back together, and they set off around the country. They end up in a Louisiana bayou, on an island where there may or may not be actual ghosts.
The movie is good at poking fun of the old series when the characters assume that the hauntings that they experience are the same as always: hoodlums trying to scare off people so that they can find some buried treasure. There is also an amusing plot line as Daphne and Fred jealously snipe at each other because of the hunky gardner and vivacious maid at the mansion they are investigating.
The animation is much better in the movie than in the old series; in fact, the credits list a couple of anime studios. The scenes with the zombies are certainly more detailed than anything in the old series, but at the same time the movie retains it's cartoonish appeal. A must-see for fans of either genre.