Open world content, when it works, helps make the world feel more alive and you are apart of it. Large, wide open areas make the player feel like they have transported to a far away planet, to a world where Crystals rule. Using this game and it's previous incarnation as an example, compared to the wide open (if bland) areas of 1.0, 2.0's open world feels cluttered and compact (if diverse).

As I said, that feeling really only happens when the open world works and there is a legit need to actually be out there. The other game I'm playing, ArcheAge and that game world his huge. It also has a reason to be that huge, because of the open world housing, limited resources, and PVP. Because the game is focused around such, their open world works.