I posted on the other threat, but to answer your questions,
1 & 2: I had severe low back and hip pain for at least a year before I bought my latex mattress. For latex to work on people with back issues, the key is to get the firmness right. People with back issues tend to report that they need a very firm, supportive surface. I *thought* I wanted a nice cushy mattress, but I ended up with an extra firm all latex mattress. Since getting this mattress, my back and hip pain has almost completely disappeared, and when I do have it, it's more on the order of a twinge rather than the previous agonizing experience.
I believe it works just because the surface is very firm, yet resiliant. The analogy some people use is that it's like sleeping on jello. If you press your finger onto the top of jello, the jello is firm, yet it gives to pressure. If you take your finger off the jello, it will spring back into shape.
3: Different types of latex can feel different. Like I said, my latex feels quite firm, but not like sleeping on a board. There is just enough give in the foam to allow my body to align and be comfortable, and because it does give, there isn't any pressure on my hips or shoulders.
4: No one can discover that for you except yourself. Not everyone loves latex mattresses. I have been very happy with mine. Jimsocal discoverded that creating his own mattress on top of springs was the answer.
5: I get tremendous body support and pressure relief. Pressure relief is this: when you sleep on a hard floor, or a very hard mattress, you feel a lot of pressure on your hips and your shoulders. This cuts off your blood circulation and numbness (or at least it did this to me). A latex bed (a latex bed of the proper firmness) supports your body and yet has some give to it, so that your hips and shoulders will compress the latex some, but it won't cause pressure against your hips or shoulders.
6. I've never had a memory foam mattress, although I tried out the Tempurpedics quite a bit. To my mind, the latex is better, for this reason. With the memory foam, you sink into the mattress and it molds around your body. If you need to move around at night, you have to overcome that crater that has been created by your body on the memory foam.
With latex, you don't sink into the latex, and it doesn't retain your body impression. If you have to move, the latex you were lying on springs right back. It's more responsive to your body moving around at night.