Steampowered Giraffe reminds me of a friend who died a couple years back because she really loved them.
weremacaque
The pillows that they made from the same material were in pillow cases and you could still feel it through them pretty easily. I doubt a sheet would help for the mattress. A mattress pad might be enough to cover the gross texture, but at that point you would have wasted money buying a gross feeling mattress when you could have bought one that didn't need a mattress pad to feel like a bed.
I went to a furniture store with a friend to pass the time before she had to pick up her boyfriend up from work, and we were looking at the mattresses since she was thinking about buying a new one. The Purple mattresses were consistently disgusting feeling. They were made out of gel material and felt like those stress balls you get out of a gumball machine. I decided to test what it's like falling into the bed and as soon as my arms touched the mattress I knew it was a mistake. It felt like nails on a chalkboard. I would never be able to sleep in one of those beds unless I was wearing long sleeves, and maybe not even then. If I had a girlfriend who had one of those beds, I'd rather fuck her on the floor or just have her come to my place exclusively. They were also selling pillows from the same company, and they were heavy and the texture was even more noticeable.
I don't usually use jelly, and put honey on it instead.