You may be misunderstanding the product--it's a topper that goes on top of your existing mattress. It doesn't replace the mattress. I do indeed have it on top of an old school analog expensive mattress. It cools/warms to the desired temperature without impacting the comfort from the mattress. I don't think there's much room for snake oil here: it pumps cooled or heated water through the mattress topper. There's no mystery.
How does it feel? I have a nice foam mattress and I'd hate to buy one of these and have it feel like I'm sleeping on a bunch of tubes and plastic rather than foam.
I can't feel the tubes at all. It does have some electronics stuff on the sides that you can feel through the topper, but nothing on the top where you sleep. It maybe feels slightly firmer than the mattress feels without it.
