I love my Xtherm. It has made sleeping in the out-of-doors much more comfortable for me. I love it for winter camping, especially. I don't know what the R-value is for that mat, but it is got to be up there. Well worth the extra weight and set up hassle IMO.

"For joy of knowing what may not be known we take the golden road to Samarkand."
James Elroy Flecker