Royole beat them to the punch by half a year. Yes, theirs was even more terrible, but at double the thickness (not to mention double the price!) of normal phones, with a ridiculously huge bezel around the exterior display for unknown reasons, and an incredibly stupid near 1:1 display ratio when unfolded, the "Fold" is aptly named. Samsung needs to go back to the drawing board.
If you look at the demo, there's a bright line evident in the middle a lot of the time, and the two halves have different color/brightness indicating it isn't opening perfectly flat. The fact they didn't let anyone see one in person - even behind glass - is pretty telling.