So I thought I'd look into this (in a manner of speaking).
First the "needs improvement". The sheer clarity of the vision you get from Carl Zeiss standard lens means unfortunately you do get up close and personal with pixels in Cardboard mode watching YT 1080p or greater res videos.
But this is mitigated by the great picture and FOV you get for a completely portable headset. For the price you pay, it's a great little headset for the Galaxy S5 (and others if you can 3D print or order their trays.
Good buy great buy.