Beware of mold growth, and tempurpedic rocks (almost):
I used to use a foam mattress on a hard wood floor,
Water condensed on the floor, the mattress got wet and grew mold on the bottom.
I built a 3" high wood frame for it too late, the damage was done.
I replaced it with a new tempurpedic Advantage, nice mattress, but was too firm for me.
Fixed it by putting a medium density memory foam topper on it:
http://shop.bjs.com/Sleep-Innovations-C ... ewprod.htm
New memory foam fumes were too strong for me, caused nasal congestion.
I let them air out for about a week (until the smell was gone), and now they are great.
The label said they are made out of polyurethane, same stuff in indoor house paint,
that explains why they smell like paint too.
Having a mattress low to the floor (and movable) makes CPAP hose routing a snap,
just put the machine on the floor at the head of the mattress.