The only problem I had was the blatant stealing from Romero's Dead trilogy. First act was like Night, with a lone protagonist wandering about, oblivious and meek to their surroundings. Second act was like Dawn, with the gathering of refugees, supply hording and search for safety. Final act was like Day, with the protagonists having more to worry about than zombies (don't want to spoil anything, but uh... I probably did) and the similarities between their respective endings.