For me, 3.5" is definitely on the small side. I'm in the 6'3"-4" range and have pretty big hands, even for my size.
And operating a phone one-handed, 4.3" is about the largest I can go before I struggle to reach the top corner of the display without struggling (or accidentally bumping the screen with the inside of my thumb). On my father's One X, there's no chance I can reach the top corner of the screen using one hand. That may not bother some but I think it testifies to the fact that the optimal screen size for most hands is somewhere in the 4" range and that anything more than 4.5" is sacrificing usability for screen size. Again, that's not necessarily a bad thing because your preference might be for screen real estate over one-handed operation but it's certainly not a useful feature from a pure functionality standpoint.
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