Jennifer's Body has a great idea at the core and has a couple more interesting ones on the outskirts. But the execution is really botched. Diablo Cody is not Joe Dante, and the people reading her dialogue need to act as if they aren't embarassed by it. Only Adam Brody pulls it off. Sadly, he is only in the film for 20 minutes.
Even Shorter Version: Finally, all you people that wanted Mean Girls and Cronenberg's Rabid to be the same film, only scripted by Diablo Cody, you got your wish. For everyone else who enjoyed Tina Fey's wit and Cronenberg's incisive mix of empathy misanthropy, stay far far away.