Picross 3D shows how DLC is done right. End of story.
i'm not familar - what did it do?
The game comes with a huge amount of puzzles (about 400), so it avoids the biggest annoyance of DLC: The game feeling incomplete. Even if you have no access to DLC, Picross 3D is well worth its money.
Right from release day, Nintendo offered a bunch (usually four or five) of new puzzles every week, for free. In addition to that, they held monthly competitions where users could send their creations (the game has an editor) based on a specific topic to Nintendo and the ten best ones were then available for download after the competition ended. So over the course of a year there were another 250-300 puzzles added to the game. I think you can only save up to 240, but it's not that big of a deal.