Despite it's linearity, I really enjoyed this game.
There are a lot of complaints about the linearity of this game, but I personally didn't mind this too much. In the game, the l'cie are being hunted by the army (sanctum), and the main characters are on the run. So it only makes sense that the characters don't have time to stop and explore. Once you reach chapter 11 (no spoilers), there is a LOT of exploring. You suddenly go from areas that are straight lines to this huge field with tons of cool places to explore. unfortunately, if you don't like linearity, you will have to wait 10 chapters before you reach this point.
The battle system in this game is very fast paced. The best way I can put it is imagine a combination of FFXII's system, and FFX's system. In the first 3 chapters of the game (the game is divided into 13 chapters), the battles are all fairly easy and can be completed by simply pressing the auto-battle button. But once you reach chapter 4, the battles become satisfyingly difficult and take a lot of thought to complete. My only issue with this was once you reached chapter 12 (no spoilers), and suddenly the monsters become PAINFULLY difficult, taking sometimes 20 minutes to defeat (not to mention the bosses which in some cases took an hour or more).
Lastly, I loved the music in this game. It's different from some of the older final fantasy games, but still gorgeous.