No 3D. It hurts my eyes so badly that I can't even look at the screen - even on halfway. The maximum I can have it set to is the lowest setting, but even that eventually gives me a headache.. so ye~ah. Couldn't do it even if I wanted to.
I generally like it, but I can't use it for extended amounts of time. I am finding it very helpful for bug-catching though- my depth perception is lacking, so the enhanced dimensional perspective is useful to me.
You need a half and half option. I turn it off when I need to concentrate better (since the screen goes fuzzy if moved too much) but turn it back on otherwise since it makes it look more 3D-ier. '_>'
I rarely if ever use 3D on any game I play, even when I do turn it on, I usually turn it off after a few seconds. The only reason I even own a 3DS is because of the AC game. I was fine with my old DS and DS lite. I do love my new AC 3DS system though.
3D has been off on my 3DS 2 hours after using it on day one (No on Animal crossing, I mean from when I first got my 3DS last year) Its ok, but I like my image sharp and clean.