I think it's a vastly better game than the first. I agree on the music, though there's definitely enough good-to-great tracks here. I don't care about story in jrpg's anyway and feel the same about the characters. Had they been better then yes, it would have been an even better game, but it's a very minor point imo. What the game sets out to do it nails.
The world of Mira is nothing short of a spectacular achievement in world-building and the exploration is just stellar. It's a rare game where just finding new areas is enough of a reward. For me the best part is how layared it is, first you're forced to explore on foot and after getting a feel for that you get your Skell, which just gives you an entirely different view on the world and after 30 more hous you can freaking fly. The sense of achievement is fantastic and you're rewarded for your hard work in a spectacular way. I also love that flight isn't this magic thing, you still have to be very careful with fuel and your HP, so it's not something to take for granted.
Honestly after all the somewhat negative reactions I heard after the Japanese release I had my expectation set a lot lower, but that proved entirely unwarranted. It's a different beast from the first game, but for me personally it's all the better for it. I can definitely understand the other side of the coin, but it's a very person-to-peron game. The reasons people give for not liking the game are perfectly fine, but if you don't necessarily care about those aspects and are in it for the gameplay and exploration, you should think this game is pretty damn great. I do.