We’ve had one for 12+ years - had a waterbed prior to that which we loved, but the quality was going downhill: our first liner lasted at least 5 years, but after that we were replacing them about every two years or less.
It took my husband a while to find a setting he could live with, he hated it for a while. He got used to it.
It comes with a plastic panel “box spring”. Those do not work well on a wooden slat-type of bed. We originally had a plain metal bed frame that provided adequate edge support, but when we got a nice wooden bed where it has side-to-side slats to support the springs, that put enough pressure on the plastic that it crumbled it in places. All our weight was on 6 4-inch-wide spots because of the slats. We got a replacement, same thing happened. We finally bought a regular box spring instead - which defeats the purpose of that nice, lightweight and dis-assemblable base, but it hasn’t required replacing yet either. If you have a slat-type bed, you’ll need to either get a regular box spring or put plywood underneath the plastic base so it has a better surface to sit on.
The top is too lightweight. We have to shove it back against the headboard every time we go to bed as otherwise it slides away from the headboard and our pillows get lost. If you had a substantial footboard that would be less of an issue.
The side foam pieces lose their shape after a while. Ours was so collapsed that I literally could not sleep in it without a pillow wedged in place to keep me from rolling out. We got replacement foam recently and it helps a lot but I can see it’ll be a problem again in a year or so (will have to try to rotate the pieces regularly to extend the life).
If the sides are vastly different pressures, it poses some… logistical issues. :D.
The mattress does not retain a nice rectangular shape. Partly because the foam wears out, but partly the nature of the beast. This means that when you try to shove it back to the head of the bed, it doesn’t ever really go flush and you will ALWAYS have a gap.
The mattress casing on the top (that holds the foam / air bladders in) is badly torn on my side of the bed, on the underneath part, which we didn’t realize until we replaced the foam. Possibly replacing that will help with the non-rectangular issue.
The advantage of the Sleep Number bed is that you can replace bits of it. Once we replace the mattress casing, the only original equipment we’ll have will be the air bladders and the pump.
I honestly don’t know that it’s more comfortable than a good quality regular mattress. I tried a Tempur-pedic when we were shopping for this one and found that to be awful; my understanding is that they’ve got a lot more varieties of those now including ones with a much softer top layer; I tried one of those in a store a couple years back and it seemed pretty nice. If I were shopping for a mattress now, I’d look seriously at one of those.