Hi, just to let people know about our experience with one of these type of mattresses.  We bought one from a local retailer, after I had a problem with my back.  We tried it out in the shop for a few minutes and agreed it was very comfortable, so we bought one.  After it was delivered, we fitted it on to the bed and anticipated a good nights sleep.  However, after five or ten minutes, we were feeling very hot and very uncomfortable.  It seemed to be reflecting your body heat back at you, and quickly became very sweaty and unpleasant. We slept very fitfully all that night.  We thought we might just need to get used to it, but it didnt get any better.  We kept waking up feeling hot and sweaty and headachey from the constant waking. We persevered with it for over a week, because it was so expensive. We felt foolish because we had tried it in the shop, and yes, it was comfortable, in the shop, while we were wearing several layers of clothes.  After over a week of not sleeping and feeling like we were being grilled on a hotplate, we returned it to the shop. It was a good quality mattress from a reputable shop and we didnt have any problems with chemical smells etc. but, despite offering good support, it just wasnt good for sleeping on!  As soon as we replaced it with a more traditional type of mattress, we slept like babies again. 

If you are thinking of buying something like this, please make sure that you have the option of returning it if you experience these type of problems.