Urban setting, classy yet nonconventional, great humor, jazzy soundtrack, lots of gang action and international influences. But, what makes it just hit my anime spot is the urban-folklore mix accented also in the OST. What can you want more, when you have a female version of a the Headless Rider, originating in Irish folklore riding on her metal steed through the city infested by color gangs and illegal immigrants from Russia :D
Each episode so far is narrated by a different charachter and the plot goes a bit highwire in a retrospect that brings everyone eventually together, because in Ikebukuro, nothing happens independently. Thumbs up!