I have only been using this mattress for a week, but so far I have found it to be very comfortable.  I got the queen medium firm and it has been supportive and comfortable.  I have back issues and so far this has allowed me to sleep with no side effects when I get up in the morning.  The mattress took 24 hours to fully expand and it opened up to 9 inches instead of the 10, but I am very happy with the performance.