A few years ago, we had two different memory foam mattresses. I hated both due to the fact that after only a short time, the "memory" part reverted to retaining the indentation where I lay. This resulted in feeling like I was sleeping in a depression, ditch-like condition. Hated it.
Started seeing the Casper mattress being advertised and decided to try it. The price wasn't any more than most other king size mattresses.
I'm here to tell you that Casper was WELL WORTH the money. No indentation retention. It's made from two separate foams, and sleeps like a dream. It comes rolled up in a box. When I first saw it, I thought "Great. This was a mistake." Now? I would recommend it to anyone.
Their warranty: If you don't like it, send it back. FULL refund. THEY pay shipping both ways.