The game has made massive improvement on functionality, but content wise very little has been added since release. 5 World NMS, 3 faction bosses, some new style leves, and some quest which give you gear for the rank that is quest is for.

In a month or 2 (maby disaster in Japan sorta delayed everything) we will be getting a whole new battle system. As others have said read the update list of what is being added it is pretty substantial.

IF you absolutely hated it before because you where bored of lack of content you will quickly quit again, if you quit because of game play issues like lag, problems buying and selling items, and stuff there is a good chance the game has been fixed for you.