The AR cards game is fairly fun. It's just a simple toy right now, but I hope it's something we see used more frequently in upcoming games. It's a little jittery at times and requires proper lighting... but when you get the conditions right the effect is pretty neat.
I think you should comment a little more on this. What little time I had with the 3DS, I was most impressed with this aspect. I almost feel like this might be the primary draw for games on the platform, not so much the 3D aspect (ironically). Just picturing AR used in game series we've known and loved is pretty exciting.
I just feel the future of this system might be in the camera technology they have. I'm actually convinced that this isn't quite the cash-in most people are making it out to be.
The AR capability certainly has a fair amount of potential. We've seen this stuff for a little while now. It was touched on with PS2's Eye Toy and used for a card game on the PS3 as well as several PS3 Move titles like EyePet. And I remember seeing videos of an NVidia-powered camera phone doing things just like 3DS' AR Games, two or three years ago. But I think the gaming industry is just starting to wrap their heads around what AR games can be and do.
For instance, it's easy to imagine using the AR on the 3DS to liven up a Pokemon trading card battle. But if you want to take it beyond the obvious, you have to start thinking of interesting ways to bring the gaming action into your real world space. AR Games' Archery was a good example of this.
How about a game where you buy several cubes, place them on a desk, then platform on top of them with Mario... as if Mario's jumping around on your desk. The sides of cubes could even have properties (like grass, lava, or ice) and you could create your own little playgrounds in real space. There are probably countless little ideas for AR gameplay, and maybe even some very big ideas, too.
One thing the AR games have convinced me of is that it would have been nice for the 3DS to have more powerful cameras. They're sufficient for some good AR fun, but I think a higher resolution would have made things a little less jittery.
I think like you, other people have been realizing the fun of AR Games, and Nintendo themselves said there will be more stuff like it in the works. I hope so. It feels like an under-explored avenue in gaming.