I’m not Phoenix, but I can help answer some of your questions.
The Nidra uses a 6" Talalay latex core, with additional Talalay latex on top of that. There is also 3" of polyurethane foam in the quilt panel. In the past the densities of the polyurethane quilt foams have been listed from 1.5 to 2.5 lb for their line, but I’m not sure of the exact densities of each layer in the mattress you mentioned (it’s been discussed previously here on the site). There has also been some discussion previously on the site regarding some impressions in the quilt foam and excessive softening, but I don’t think anything directly related to this model, and of course everyone’s results can vary. My concern would be more the durability (density) of the polyurethane foam.
The other issue you’d have, which would be personal, would be your own comfort sleeping upon someone else’s used mattress, and all that entails, versus the price you’re getting. That’s one area I can’t offer much help.
Jeff Scheuer, The Beducator
Beducation / Mattress To Go