The effect is pronounced, but seems far less distracting than you'd expect. The lack of plastic glasses imparts a level of viewing comfort that you simply don't get from 3D televisions, though the comparatively smaller screen is also easier on the eyes. The visuals are bright -- easily on par with the DS Lite -- and offer a good viewing angle. However, viewing from the side reveals the blurry, overlaying effect of the 3D screen, so you'll want to turn the 3D effect down via the slider.
Adjusting the 3D effect is a seamless, subtle act, with the depth of the 3D images -- think of it as a tunnel reaching into the top screen -- slowly reducing to 2D as you move the slider down. We had a look at several demonstrations, including a selection of Nintendo characters (think Smash Bros. trophies) in different settings. The Pikmin blended into the grass, Yoshi's nose seemingly protruded from the screen and black particles surrounded Link, almost appearing to float in front of the top screen.