From what I understand:
Everybody shares quests
The quests are chained and effect the content
These are eventually reset at the end of the quest line

It's a cool concept but not enough to change the way FFXIV's system works. I love me some good story line, and entering a quest that is already half way done seems kind of awkward.

People tend to forget the massive arsenal of innovation that FFXIV has:
Position based combat
Armory System
An upward crafting system (where various classes rely on other classes i.e. DoL->DoH->DoW/M)
Beautiful Graphics (on top of characters seeming to be lifesize... lots of MMOs have a wierd problem where the character doesn't feel as big when playing)

Even with that amazing concept of Dynamic World thing, I don't see myself switching over to GW2 anytime soon. I thought about it before I saw footage... and after seeing it.. meh