Generally I think it's good to take people's reports of their unusual mental experiences at face value, even when they're crazy. Not that they never lie, but that you learn more by assuming they're probably telling the truth.

I haven't attempted unihemispheric sleep, and it sounds like a phenomenon that isn't represented in the literature, but it also sounds like it wouldn't get past an IRB anytime in the last decades, so I assume it's probably real.