I beat it today at work (lulz).
The game starts off all emo and icky, but after the first couple of hours or so, the story really picks up and the characters really start to become far more like-able. As for the music... Well, I think there's something for everyone in this game, just that you can't ask the game to play just the songs you want it to play. I also think Tin Pin Slammer is a pretty nice mini-game.
The battle system is sometimes horrid and sometimes awesome. It's awesome because a person can truly fight any which way they want, according to their style and strategy. It's horrid, however, because of the stylus movement. Moving around can be tricky since sometimes, the game will confuse itself and think you're using one of the pins or whatever (if you have a pin that activates itself by touching empty space).
The art is very Kingdom Hearts-ish except that now, you have alot of a graffiti and street-like art coming in your way. In fact, to me, it felt as if the game was meant to be a comic book.
Also, an interesting note:
Shibuya seems to be a real place in Japan. Of course, this is only according to Wikipedia, but hey, some things may be useful, y'know? I find it interesting how It's a Wonderful World even has things such as the Hachiko statue in there (and even used it in the story!). Really nice... Kinda makes me feel as if I went to Japan already!
All in all, the game's really good, despite Swiftu's dislike of it (I mean, to each their own, and I understand his reason for not liking it) Still, I think the game's good and worthy of attention. It may seem emo at first, but after a while, you can see how the characters mature and blossom.
I give It's A Wonderful World (a.k.a. The World Ends With You) a 9/10.
(Also, I considered putting this in the topic Swiftu made, but the last post was by me and was also already on the second page. On top of that, I feel this new topic has plenty of information not inside Swiftu's topic... I hope this justifies the creation of this topic. If not, then please forgive me.)