These shoes are fantastic!  I have nerve pain in my feet and nothing is truly comfortable.  But these stretch uppers are just the thing for me.  The memory foam is a dream to walk on too.  I understand the heel slipping complaint.  But I bought mine 1/2 size large because I can't stand them too tight.  Am going to see if there is something I can put inside the heel that will keep it from slipping. Very worth the money!