I have had my Casper matress for almost a month now and I think it is great. It is amazing the difference you notice from sleeping on a Casper compared to my old matress. When you lie down you absorb into the mattress but don't sink into it. I find that I am falling asleep faster and even if I'm woken up at night I find that I can quickly fall back asleep. I wake up more refreshed than I have in the past with the same amount of sleep that I have before.
I have been using the Caspar for about two-three weeks and wake up each morning with back pain. I always slept on firm mattresses. This is entirely different. I will try for another few weeks to see if my back and Caspar agree. If not, will return it for full refund as advertised.