Hi PeterDoubt,
The Casper is a foam mattress (latex foam, memory foam, and polyfoam are all different types of foam) and contains 1.5" of synthetic latex over 1.5" of 4 lb memory foam over a 7" 1.8 lb polyfoam support core. It doesn’t have enough latex or memory foam to be included in either a latex hybrid or memory foam category so it would be more fair to call it a mattress that has “hybrid” comfort layers.
A forum search on Casper (you can just click the link) will bring up all the forum posts and feedback that mention them.
I would also be very cautious about using someone else’s experience on any mattress (either positive or negative) as a meaningful source of guidance about how a mattress will feel for you because firmness and softness is very subjective and relative to different people (a mattress that feels firm for one person can feel soft for someone else) and each person can be very different. There are also different types of firmness and softness that different people may be more or less sensitive to (see post #15 here) and a mattress that is a “perfect” match for one person in terms of PPP (Posture and alignment, Pressure relief, or Personal preferences) may be completely unsuitable for someone else to sleep on … even if they are in similar weight ranges. Using other people’s mattress reviews or experiences as a meaningful source of research and information can often be more misleading than helpful (see post #13 here).
Phoenix