As someone who really didn't care about the story from the jump, the latter half of the game hasn't bothered me. I adore the combat and leveling up jobs and mixing up abilities. The extra hours of gameplay give me an excuse to do that. I could see why others would be upset by the post-chapter 4 stuff, but I'm not. And I really don't think it's even close to being as bad as the Tiz/Egil stuff was. That section of the game was almost unbearable.
I think I just hit a point in the game (about 45 hours in) where I can really see some people getting annoyed with the direction that the story takes--and by extension what you're made to do for the next stretch of game.
I'm loving it though.
There is one pretty unbearable segment toward the Fire Crystal involving Tiz--the worst character by far. Edea more than makes up for him though. Mrgrgr.