The difficulty has been revised upwards. It's more difficult to play stealth, there new categories of enemies, and nature has never been as dangerous (eagles, tigers, hounds). You have to be armed to the teeth if you want to walk quietly on the map. The story is classic, but works very well.
There are many new features, to name a few: random events, side quests, weapons and grappling hooks. All this makes the game very enjoyable to play and we want to spend hours.
Here is a real FPS, for players who want to go in a universe without all the time to shoot at opponents in games without flavors.