Pros:

-Tells the survivors' stories from two different perspectives
-Follows the plot line closely
-Epic music (Imagine Dragons)
-Animations and cuts fit the music perfectly
-Perfect for L4D2, considering you can play every map

Cons:

-The speed at which Louis runs to the helicopter is super unrealistic (but who really cares)

Conclusion:

The best, by far, intro addon ever introduced. 10/10