Zombie Island is the first bit of DLC for this platinum selling game. It is both challenging, annoying, and fun.
Story: The developers at Gearbox Software said that Zombie Island would have a better story to it. They were right, to an extent. It had a decent story to it, but it did not effect the story of the main game.
Score: 8
Gameplay: The DLC was great. It not only was fun, but it was challenging. Zombies don't pose a threat, unless there is a huge group of them. The game was loaded with zombies, obviously, and there were many different types. This helped make it more original. The only problem was they could get annoying (BRAAAAINS missions)
Score: 8.5
Replay Value: The DLC was only 6-10 hours, which is good length. The only problem was it got quite repetitive. After doing one trip of this add-on you may be hesitant to go back.
Score: 7.5
Overall: 8
If you own Borderlands you should definitely get this add-on. It is worth purchasing.