I have the game, and I'll throw my two cents into this. ;)
First of all, don't expect this to play anything like a FF game, thats seems to be the main reason why so many people dispise it. It does have a lot of connections with FF games as far as names of magic and weapons go. And of course, the FF characters. I wouldn't call the gameplay childish. I actually don't get that point. It's one thing to call the game childish because of the characters and the worlds, but the gameplay? Please, this is the hardest Disney game you'll ever play. ;)
And the game can get challenging at times, even on normal mode. I still have to go back and defeat Sephitoth.
For the gameplay, it's all action. And the character customization can get deep. The collisum is also a great addition to test out your skillz.
And the game does feel more like a "Square" game around the mid-end.
Also, this game has one of the best endings ever. And the secret ending is to die for.
Overall, you should atleast give this gem a rent.
Hope that helped. Ask me any more Q's that you might have.