As good as it described.
I has experience this at my flat during winter without any heater on. The temp. gone down to 4C, and it still keep my back warm. Some criticism about the plastic paper noise when moving the body on it, I didn't experience this.
Compare to the sleeping mats which I got previously from the big brands, the only down side I can spot is lack of structure, the material seems to be softer, given it is 12cm thick, softer material perhaps lighter but it does scarify stability, for a thicker mat, I would prefer more structure. Lucky the mat is wide enough to compensate the stability issue with soft material, and it does secure at my back throughout the night.