Detail and Scope of the world. Though, if I could pick two, I would definately pick cramming crap into my inventory as number 2
I can't even begin to imagine playing and not being able to sit there, with a full inventory and say to myself "Is this item really worth its weight? I could drop this, and pick up that, then I would lose 10 pounds..." lol. And then, if it comes down to it, I just use TGM to carry loot to a city... its not REALLY cheating, its just saving me the time of running back and forth