I bought a Nature's Image natural latex mattress in March. From the first night, I have noticed that I fall asleep faster. In fact, I've been sleeping better, and I don't wake up as much during the night. I have had lower back problems in the past, and I used to wake up feeling stiff with my old mattress. But that is not the case with this one. In fact, I have had no major back flare ups since I bought it.
However, I should point out that I weigh only 146 pounds. This kind of mattress may not be right for heavy people. I think a lot of the poor reviews about this kind of mattress come from heavier people. You may have noticed that the Tempurpedic gets a lot of negative reviews too.
I don't sink into this bed much, so I have had no problem with heat. However, my bed is the plush kind, with no pillow top. I've read that latex is springier than memory foam. The bed contours to my body, so when I roll over, I sometimes feel like I'm rolling up hill a little, but then the bed quickly adjusts to my new position. That took some getting used to at first, but now it really doesn't bother me at all.
One side seems softer than the other, but that's only because I sleep on that side. When I've moved to the other side, that side softens up a bit and contours to my body as well.
All I know is that I'm sleeping better, so I think the bed is working for me.