I suspect the memory foam is very comfortable for people without back problems. It feels comfortable, except for the effect it has on the back, as you sink into it.
This is why I sleep on a thin pad over a board. It keeps my back supported. It isn't as cozy as a feather bed, but it keeps my back in line.
Are you a side sleeper as well?
Yes, although my contortions are rather singular, due to the nature of my lumbar injuries. Sleeping on my back or belly just isn't possible.