I have to say, The World Ends With You is rapidly becoming one of my favorite games on the DS, maybe even a serious contender for my game of the year if the year didn't already include GTA IV.  I think this game may have slipped under the radar of a lot of gamers but give it another look.  Among the things I love about it:

-- Very interesting setting, modern day Shibuya but... not quite.

-- Exciting combat system that really uses the DS in a non-gimmicky way.

-- Great (if sometimes repetitive) soundtrack.  A particularly rare comment for a DS game!

-- More zany mechanics than you can shake a stylus at.

-- You get to read people's minds and make them say inappropriate things!

It's all quite polished.  I think this is probably the best thing I've seen out of Square-Enix in a while...