Wow, you literally sink in the middle and can hardly get in or out of the bed!  Bought a 4" firm topper for it too and it still sinks!  A $1,000+ purchase I so regret and not feasible to ship back a KING mattress especially when the company doesn't make that process easy either.  I hate the mattress and wish I was able to go to a furniture store and tried it out instead but that wasn't possible at the time and for a lot of other people too.  Don't order a mattress online.  Lesson learned.