I keep seeing them mentioned, but only recently, they must be a new thing.
What is the point? How is their effect different from a good electric blanket and high TOG duvet? Can you use them with an electric blanket?
I see them recommended as good for snuggling on the sofa, but I am more interested in their use on the bed and whether there is any point in suggesting one as a Christmas present. It might help DH avoid his usual panic stricken Christmas Eve trip to Boots hunting for something scented.