Awful. We got it to replace a 20 yr old S&F. This mattress is a work of pure evil. Underneath you is some sort of material that resembles a thin wool blanket. It will keep you very hot. I've tried sleeping on it for 3 nights, I got 3hrs one night and 2 x 5hrs before being woken by furnace like temperatures. How much of that was REM God only knows. If you like to control your body temp and 'security' by way of your own blankets, seriously look elsewhere. You'll likely find that you'll need to pitch your blankets off which in turn will leave that part of your body getting gradually colder. Their sales documentation states that the mattress takes heat away from the sleeper, that's a lie and false advertising.