Because of my bad eyesight, I can't use the 3D option. >w> In order for the 3D to look good, I have to hold it far from my face, but then I can't recognize a lot of details. Not to mention it's kinda uncomfortable to hold it away for too long.
Same here, I knew I didn't like the 3d before buying the 3ds and probably would of bought a 2ds if it had the same design (flip closed) if they had not had ACNL and Pokemon X I wouldn't of bought at all.
I never play this game (or any game really, for that matter) in 3D. It makes me dizzy when I use it, and I almost always forget the 3D feature even exists in the first place. Animal Crossing: New Leaf barely uses the 3D effectively anyway (at least it's better than it is in Pok?mon X/Y though), since the text box sticks out like a sore thumb (it appears closer up than the rest of the game).
Maybe for a few minutes, in Katrina's, during a PWP ceremony or when cherry blossoms are flying, but 95% of the time, no. My ADD prevents me from sitting perfectly still enough to maintain the right angle.
The only time I turn on the 3D feature is when I'm taking a picture and then I turn it off again. With the 3D on, if you move the console or your head slightly then everything is fuzzy. But it does look cool when you are getting your fortune read by Katrina.