I normally keep it off, especially for Pokemon XY/ORAS. They dont use the 3D effect consistently. When they do, primarily during battles, the frames drop like mad. So I keep the 3D off.
I don't really care about the 3d either (reason why i almost opted for the 2ds but didn't want tiny screens) but i did use it a few times with Mario Kart 7 when i had it and i just felt like it was a gimick and it's hard to keep your head in the sweetspot so i keep it off. Plus it drains the battery quicker and the 3ds family doesn't exactly have the best battery life especially compared to the ds lite family
i do on some games, esp the battles in pokemon and like when there are words throughout the entire screen, idk i just wanna feel the 3dness but when i play casually, not really
I would keep it at like 50% 3D all the time, but having to keep the 3DS directly in front of me turned me off from doing that. If the New 3DS XL happens to make landfall in North America, I may just get it as it seems to be doing a lot of things that the 3DS should have been in the first place.
I don't use it for most of the time, but I do if the game is in a cutscene or something. Or if it's something I feel like looking at in 3D like epic scenes in Pokemon.
I've never bothered with the 3D, ever. Although sometimes I might accidentally flick the 3D option on by mistake, but the minute I realize it's turned on, I turn it off again. It just doesn't look that appealing to me.
I bought the console for the games, not the main feature this time.
Probably 80% of the time. Most of the games I play don't seem to bother me, but that 20% included Animal Crossing, Pokemon (for which it got annoying flipping back and forth so we 2D'd it) and times I play with friends cause we can't sit still and it makes me dizzy flipping around like that.