That being said, it'd be nice if there were at least a few, REALLY big open areas, for rare high level mobs (Lvl50+), maybe super high risk treasure hunts, and massive scale combat, for large scale PVP, massive Fates, etc.
That, and just because a few large open areas would be the world feel larger, even when you were outside of those areas. I mean, sure, because of PS3 limitations they wouldn't be able to make these areas quite as pretty, they'd have to reuse textures and models more frequently. But, for an endless grassland, or an perpetually misty forest, that wouldn't be much of an issue.