I had a knee-replacement operation on my left knee in July and the primary reason I bought this 'Full'-size 14-inch-high mattress about two months ago was to try to get more comfortable sleep with less pain in my left knee and left leg. Sure enough, I'm finding the mattress pretty comfortable and it supports my leg well, leaving me without much pain. However, I notice the gel foam layer isn't the same thickness throughout every part of the mattress (or at least the cording round the mattress supposedly at the bottom of the gel foam layer isn't the same distance from the top of the mattress all the way around it). I'm also finding the left side of the mattress a bit firmer than the right side. Although both sides are comfortable to sleep on when I'm lying on my right side, the difference between the firmness of the mattress on the right side and on the left side is making it rather difficult for me to sleep on my left side and angled across the bed somewhat (as I like to do), because it feels rather like I am sleeping down a hill, with my left side higher than my right. This tends to turn me on to my back, a position in which I don't like to sleep. All this makes me think that these mattresses are really slight seconds, rejected for full-price sale. That said, the mattress I purchased is pretty comfortable overall and the gel foam layer helps to keep me feeling cool when I'm sleeping!