How bad is it? Absolutely wretched acting in a bloodless zombie film.
Should you see it? A soft no. there's a couple of laughs, but it's a long wait to get there.
Zombies created by a diet pill force a family to barricade themselves indoors with visiting relatives that are so obnoxious you'll scream: bring on the zombies! Also at the party is a Santa and some elves, who just might be the real deal. There's a sudden jump to the President and his cabinet in a bunker (or more likely the basement of the house in which the film was shot) who plan a rescue mission - preferably not involving nukes - and they've discovered that light will stop the zombies, but they'll learn to adapt; this could've led to an interesting plot, but gets abandoned. Instead, Santa takes on the zombies by shooting Beanie Babies (given another name, due to copyright) at them and, when he runs out, to stall for time, the zombies are invited to sit on Santa's lap and tell them what they want!