One of the New Nintendo 3DS's most welcomed added functions is head tracking. Its purpose is to help make the 3D effect more stable, and you know what, so far, the function seems to work pretty well.
In the video you below, you can see me testing the head tracking software. Keep in mind that the video is, of course, in 2D.
I like how the New Nintendo 3DS tries to adjust to your positioning, making the 3D effect more comfortable than it's ever been. Good stuff, Nintendo.