Interesting. I tried the "space blanket"(bag) thing some time ago, and sort of decided their real virtues were lack of weight and bulk, with anything else far behind. I found "sleeping" in the cold with them slightly more comfortable than dying. Maybe.

I find the Thermo-Lite stuff far more useable:

http://www.campmor.com/webapp/wcs/stores...productId=99840

Still pretty cheap and small (stuff bag pictured is not to scale- check specs). Not perfect, but it's much more comfortable and vastly more durable.

I wonder how they'd do in the water? They are somewhat more permeable, which might be a slight negative, but they might be durable enough to actually work in real-world conditions.