I have two of these mattresses and I will probably never own another one from anywhere else.  They are just the best mattresses I ever had and after two years they still don't sag, they still sleep like brand new.  I recommend them to friends.  But if you ever have to move them or flip them around, get ready.  They are SOLID.  All those coils make these mattresses stand up on their side and that's the only reason one person can have a chance of moving them.  That's how heavy and thick they are, yet they sleep like a dream.