I certainly lost interest in the 3DS as soon as I heard about its 3D Focus. I bought it despite (!) 3D after KH3D came out and after some tryouts I always play without 3D. For me it is as useless as the stylus controls because both do not offer anything valuable for my personal gaming tastes (well, the stylus controls work with games like Phoenix Wright and Professor Layton... but it ruined "normal" games for me. I had a hard time with TWEWY for example.)
One can quote the 2DS as a source that the 2D version is not that desired, but for me it simply has an ugly design... I bought the 3DS instead despite not wanting the 3D feature.