I thought memory foam would be a great mattress.  A sales lady had me lie down in one and attempt to roll over.  It was like trying to roll over in loose sand.  Then she informed me that they're often hot, and showed how a company was advertising theirs as the "cooler memory foam" mattress.  I turn into a furnace when I sleep, so that one is not for me. 

 I agree I have one too and these hot weeks I'm dying of sweat