I have been sleeping on this mattress for a week now and could not be happier. I have lower back pain and am a side/back sleeper. This mattress hugs every curve in just the right way. I have had other mattresses that grew to be comfortable after weeks of breaking them in. This mattress was perfect from day one. I slept on it the same night I pulled it out of the box. It reached its full size within minutes (I was frantically cutting it out of the plastic because it expanded so quickly). There was no smell. I slept on it on the floor for a few days and then on a boxspring and frame. I didn't notice a difference when it was on a box spring so unless you are looking for height I would say you don't need one. I could not be happier with this purchase.