You ask what ABers' choices are.
Mine and my wife's is along the lines of gingejbee's, we hate springs and memory foam. We have beds in three different places and the mattresses, all 2x2m in size, are all the same, the oldest being approaching 15 years old and is utterly unchanged and likely to last another 50 years anyway. The material is often called Frostex, although that is probably just the best known manufacturer of this type of foam. One of our beds' mattress is slightly firmer than the other but we sleep just as well on it as on the rest. In the beginning I was looking for something firm to go on our totally flat beds (it is established that flat beds are the best way to avoid/combat back troubles - the main reason for avoiding springs which ultimately result in sagging, and bouncy, beds). After choosing I was filled with fear - too firm, I was convinced. To test whether pressure points would be felt I lay down on it, intending to be there a while. I woke up some 15 minutes later - a pass ! The mattresses are a mere 4cm thick and each cost us somewhere around £100. Our younger son was brought up on one of the same type which he takes with him as he moves from country to country and describes sleeping on anything else as torture.
Just one preference example.