The technology page makes me thing the viewing angle is going to be more narrow than e-ink; the shape of the surface and the difference in index of refraction when on and off is going to determine how well they can do on that metric, but the complete lack of any mention of viewing angle makes me think it's not great.

[edit]

https://youtu.be/zjJ2-cdhwMQ?t=219

It's B&W and much lower contrast than current gen e-paper, but viewing angle looks great (maybe 120 degrees confirmed from the video?). They definitely need a matte surface though; that glare was terrible.