Factual error: When the zombies are about to over-run the house, one of the ravers sacrifices himself by shooting a keg of gunpowder to blow up the building. The problem is that gunpowder is not an impact explosive, you could shoot that keg all day and all it would do is put holes in it. Just shooting it would not cause an explosion.
Factual error: Within minutes of encountering the dead, the survivors are handed out guns and artillery and immediately know how to use them without any training. Considering the size and caliber of some of the guns they use, I doubt they would be so proficient, or calm, after less than a few minutes of using guns.