This is the best multiplayer game i've ever played.
The new maps are awesome and now, it's harder to level up than on his predacessor.
They changed some weapons, added new weapons, improved and added some new features in the game, like:
zombies
They improved a lot the zombies mode and it feels like a seperate game.
In the zombies mode you start with a basic weapon and every zombie you kill give you points that you can buy with them new weapons.
You can also turn into a monster with special abilitties like an electric shoker.
co-op campain
Now you can play the campain with your friends!.
new abilities
Every player can have a special ability.
There are a lot of abilitties like:
Purifier-a flamethrower that you can burn and kill people with it.
Sparrow-a bow that shoots explosive darts.
Tempest-a kind of a shotgun that shoots electric boolet.