I've been debating between the memory foam and the "sleep number" bed. Has anyone ever used one of those?
Yes, one in my bedroom.
To me, an adjustable bed makes about as much sense as adjustable shoes.
Well, I have a son with a misaligned hip bone. He has to adjust one of his shoes by placing a wedge inside to lift the lower side of the hip up, thus alleviating his back pain. The more expensive solution is orthopedic shoes, kind of an adjustable shoe...
To me, it sounds like one of those things that sounds good in theory, but doesn't work in practice. That's why I was wondering if anyone had used one. It seems kind of like an overgrown air mattress to me.
Yes, it is an air mattress. It works wonders! I wouldn't have anything else now. For the first time in my life, I can actually lay on my back comfortably for more than a few seconds. But, I sleep mostly on my sides. (one, then the other - not simultaneously)

On any other bed, I wake up sore. On my sleep number, from Select Comfort, no more aching!
For couples, the ability to adjust each side of the bed separately could save the relationship! My wife sets her side at 70 and I set my side at 30. They say the average is 65. (It can be set in increments of 5 from 5 to 100.) For years, she told me that a firm mattress is best for your back. Only after getting the SN from SC did I realize that it was the best for
her back!
Recently, we spent the night at her parents house, and had to take the room with two twin beds. I laid down for about 15 seconds, and knew there was no way I could sleep on that slab of marble. I spent the night in a recliner in the family room!
They advertise that the cost of a SL is about the same as a spring mattress. I don't know how they get away with that. It's not true. But, it's well worth the extra cost. They also say it will last twice as long as a spring mattress. The jury is still out on that one, in my experience.