We have a Serta I-comfort which is Serta's memory foam mattress, I have the one with the cool gel layer.
I love it ... my husband not so much. We both agree it's tremendously comfortable, but he thinks it's too hot. It should be noted however that my husband thinks a regular spring mattress is too hot. I agree that my husband is indeed too hot in bed (and no, that was NOT a rude comment, I'm talking pure fahrenheit here!).