The most famous maker, Tempur-Pedic, says this about the qualities of the visco-elastic foam:
The material has been engineered to react to your body through a very specific range of temperatures. It becomes softer in warmer areas, where your body is making the most contact with the surface, and remains firmer in cooler areas, where less body contact is being made.
The reason for this post, however, is that DWR's new Sonno Prima Mattress is made out of the same stuff with better workmanship around the covering material AND it is cheaper than Tempurpedic. DWR = $1,195 and Tempur = $1,500, which is what we spent five years ago. OHR/MGR