This is a little divergent from the original question, but it is an endorsement of a product that is *great* in my opinion.
We have one of the Select Comfort beds. My back is *so* much happier. It takes a bit to get your firmness tuned just right and to get used to a mattress that conforms, but WOW! What a difference. The even pressure makes a huge difference.
They know how to sell these in the Select Comfort stores....they put you on one and air it up until you tell them that it feels about like your current mattress. They then let air out until you tell them that you can feel the pressure even out over your body. They let you lay there for a minute or two and then run it back up to the number you were at when you said it felt like your own bed.....which then feels like a brick with sheets.
We come home from vacations where we have been on a variety of other people's beds and go back to it and say ahhhhh!
They have an outlet store, too that sells beds that were returned during the trial period. They completely replace the whole mattress cover so the only thing that has been anywhere else is the innerds (air panels) and the inflator. They cannot sell these to some states that have laws against the sale of used bedding. We saved quite a bit on what is otherwise a really expensive mattress.
I have no connection to the company other than being a very satisfied customer.