Battle pieces are pretty nice, but the rest of the soundtrack was pretty blah, if you ask me. Oh, and the nice vocalized Chocobo theme was cool. Otherwise, some of the music feels really out of place; I remember one spot in particular made me feel like I should be in a coffee shop talking about something abstract over a Grande Caramel Mocha with extra whipped cream, and not in an area where things are blowing up in my face.
I'd say while it's not bad, it's probably my overall least favorite soundtrack of the (main) Final Fantasy games. Unless you count X-2 as a main FF game. Then FFXIII's OST is second-least favorite.