Day Z, the popular ArmA II mod, have revealed some of the features that will set it apart from the original.
The chief improvement will be the inventory system. According to the developer, it "supports crafting, interchangeable clothing, degradation, tracking, weapon customization, and much more." In addition, when looting players must scavenge inside of vehicles, look for items stuck between furniture, pry open car boots, and so on. "Consuming your bounty now results in rubbish, such as empty cans after consuming your beans," warns the developer, "This is no mere gimmick, because your trash can be used to track you."
Eating becomes part of an expanded health system that takes into account physical health, blood, and consciousness level. "Some of the exciting developments coming include longterm play effects such as poor diet affecting your long term health levels," the blog notes.
Finally, there are major improvements to the environment and the zombie behavior. Cherno will be expanded to add two new villages. In addition, the top (north) map area will be bigger, and large-scale features are continuously being added to the map. Zombie pathfinding is being improved, and all zombie spawns will be server side - partially for security against hacks, and partially to prevent zombies "popping" onto the landscape.
Check out the developer video blog for some visual demonstration of the improvements.