Experience with Tempur-Pedic-type mattresses?

Have you invested in one of those engineered “memory foam” mattresses to improve your sleep? If so, what has your experience been? I’d rather talk to knowledgeable customers than to commission-seeking salespeople.

On the one hand, something that would ease my sleep (including not transmitting shock waves from the other side of the bed) would be better than living in a mansion. On the other, I am afraid of anything that would maroon me in one position for too long.

And I can’t risk making a big dollar investment in something that might not work. How can you tell in a few minutes’ trial in a showroom what it will be like after six or ten hours?