A lot of reviews on here don’t mention what size or thickness was selected which I think could make a huge difference. I purchased the 8” thick twin and have had it for about 6 weeks. The memory foam is quite soft and nice though I could use more back support at night. For $100, this is a great mattress, and I’d buy again. It replaced a nicer Ikea foam mattress that i found too hard though in retrospect I think a cheaper firm/hard mattress paired with a decent/nicer memory foam topper is the way to go. Expanded to full, even thickness immediately and was ready to go. I imagine those whose did not expand as advertised got defective products and are due refund/exchange.
ETA: 14 months later, this mattress is still amazing! No topper used, and I still get a comfortable night’s sleep every night!
ETA: 26 months from purchase and this mattress still holds up just great 😴