I got a latex mattress on-line & felt it was not supportive enough--especially since I was used to the traditional spring mattress & boxspring. I ordered this Rejuvianator because of the high content of foam. We put it under the latex mattress and it's done the trick! It provides a good amount of support and "heft" to our mattress & bedframe. Sorry I can't comment on the use if it's on top, but there are plenty of those reviews. It did have a bit of a "nail polish remover" odor, but we let it puff up outside for the day before we assembled it on our bed. It's a tad bit short on my side of our California King bed, but only by about 1 inch.