Licensed roguelike outings don't always turn out so well, but Chocobo's Dungeon works far better than the likes of Pokémon Mystery Dungeon -- the perfect delta of hardcore dungeon crawling and the world's most popular RPG series. The Final Fantasy trappings are more than mere window dressing, yet they complement the underlying genre mechanics rather than compromising them.
It's definitely a game for RPG fanatics who go in more for the challenge than the plotline, and no doubt casual players who pick it up for the oh-so-cute cover art will be rather surprised by how brutally it savages their dignity (although a generous learning curve should help ease them into their suffering). Still, it's a definite success, taken on its own terms. The only question, really, is whether or not gamers are ready to accept those terms.