We just got a Purple Mattress about a month ago, and absolutely love it. There are different firmness levels, so you'd have to go try it out. We came from a Tempurpedic, which I did not love because the memory foam often took 20-30 seconds to settle and hold your position. The Purple simply and immediately holds you in whatever position you are in.
Of course, we also got the adjustable moving bedframe thing, which is cool. Wife loves the Zero-G position when she's reading in bed. However, my favorite thing about the frame is that it has a motion sensor night light underneath, so if / when either of us has to get up in the middle of the night, it lights up the floor without disturbing the person still sleeping.