I purchased a memory foam mattress for my husband who has neck and back issues, however he is deployed so I can't give you his review just yet.  So far, I'd say I LOVE IT.  So much more comfortable than our old spring, pillow top mattress.  I also like that when my kids summon me from my beauty sleep at the  crack of dawn for breakfast, they don't shake the entire bed-seems to absorb the crazy.  I sleep better, and I am not sore when I wake up.  I would have given it 5 stars, but I am finding it difficult to keep my fitted sheet on.  I think I may have to pin it.  I'd recommend it though...no less than 10"..I think anything less and it wouldn't be as comfortable.  Anything more and I feel like it would overwhelm our platform bed.   Don't forget to get a mattress protector for it-can't imagine how it handles sweat...  *shiver  gross.