Strange to say but the problem is because its glasses free. 3D work by having a distinct image to each eye. Glasses makes 100% sure each eye get the image signal at the right place, because each image is diffuse at a 180 degree angle while being block alternatively by the glasses fast enough that you dont notice it. You can move and change position and still get the same 3D without ghosting effect. While a glasses free device need adjustment, and if you move, which is going to happen while playing on a handheld device, the image will not focus at the right place.
Tough, this doesnt apply to all glasses free device, the TV made by phillips (technology too big and expensive to use in handhled for the moment) displays a distinct image to each eye inside a wide radius. It diffuse 2 images at multiple and different degree from each other. Those display doesnt need adjusment and will not give nausea or ghosting effect as it is a natural way of seeing 3D.
Philips tech:
