I have the Queen medium firmness Serta Perfect Sleeper Pacific Peace mattress. To me, the matress is still a little too soft, but I am not sure if it's because of the memory foam layer it advertises. But I also feel that the mattress makes you a little bit warmer despite it being advertised as having a cooling layer. I think the softness of the mattress makes you sink in more, covering more body surface area and causing you to feel warmer. I think I should have gone with a Firm mattress instead and it might have been perfect.