In addition to having one of the coolest titles ever, The World Ends With You is downright amazing to play.
The story is fantastic, the art style is right out of Kingdom Hearts, the music is memorable and very well implemented, and there are tons of additional game-play mechanics to extend playability. But perhaps, most importantly, the execution of combat via touch screen mechanics (tapping, scribbling, swiping, blowing, etc) is just about perfect once you get your head around it. It's fast, explosive, and a hell of a lot of fun.
I really think that the Kingdom Hearts team is making some of the most exciting and original takes on the traditional JRPG. It is a real treat to see them produce something new and have it come off so successfully.
TWEWY is a must buy for nearly all DS "gamers".