This is one of those movies that is worth watching purely for the enjoyment of watching terrible actors do terrible things in a terribly plotted horror film. It was probably one of the funniest films I've seen in a while, simply because of the twisted enjoyment you get out of a film that is this awfully bad. However, it is respectable because at no point does it pretend to want to be taken seriously. Everybody in the film (except maybe a select few) and obviously everybody working on the film knew that it was God-awful, giving it a sense of irony and hilarity seldom achieved.
The hard-ass lines uttered by the members of an elite zombie fighting squad are especially awesome, as is the premise that the government is releasing a zombie virus upon its citizens. It's kind of obnoxious when it attempts to actually be a legit political commentary, but it's really, really funny when it's simply making fun of the premise and how stupid it is.
This was one of the most enjoyable movies I've seen in a long time. However, go into it with a sense of humor. I honestly didn't stop laughing the whole movie.