It's brilliant
There are no sidequests for the first 20 hours, but then it opens up, and as I understand there are plenty of post-game things to do. Not quite as much as FFX, but better than most, certainly 100 hours of entertainment
The eidelons are fairly useless, like aeons in FFX, but that didn't harm the game
The main point, is that the battle system is just fantastic. It is linear, but still very fun, and it does open up towards the end