Well, you certainly won't be sleeping as "cool" as their clever marketing would lead you to believe.

I could tell you what you want to hear and just repeat the typical unsubstantiated claims from manufacturers, but I'd rather give you a heads up (and tell you what you won't hear in mattress stores) which is that gel-infused memory foam doesn't help one bit to keep you "cool" while you sleep. There isn't a single peer reviewed scientific study that proves that gel infused memory foam works to keep the mattress cooler.

On the contrary, independent testing has revealed that these sorts of claims are unsubstantiated puffery. In fact, this is why Serta was asked by the NAD last year to discontinue their "cooler" comparative claims from their iComfort marketing, which uses the exact same gel-infused memory foam as the iSeries.

The next time some salesman tells you that gel-infused memory foam works to help sleep cooler, ask for evidence. But to answer your question, it would be impossible for someone to tell you "how warm" you'll sleep on a bed since there are too many variables.

Source

The Serta iSeries mattresses all have at least one layer of Cool Action Gel Memory Foam in them which is designed to help you sleep a little cooler than an equivalent mattress without the gel infused foam. The Initiative Plush doesn't have a lot of layers, and the gel foam is on the top, so it should stay fairly cool. Some people sleep warmer than others, so there really is no answer to the question, "how warm"? I hope this helps!

Thanks for spurring some healthy discussion on this Sean. We definitely agree that consumers need to be careful in terms of setting their expectations on this front.

Personally, I think the key thing to understand is that there are many factors that determine how warm or cool someone feels at night, some of which pertain to the sleeping environment and some of which pertain to the sleeper themselves. In any case, the mattress is not likely to be the biggest factor -- not by a long shot. And, even if you focus in on the impact of the mattress itself, whether or not it has gel is not likely to be the biggest determinant of whether it sleeps warm or cool. There are other factors that are equally or more important, like how deep you sink into it, whether it has memory foam at all, etc.

Based on these factors, we would estimate that this particular model might have a 'slightly warming feel' but that this is very unlikely to be a problem for most people -- unless you have a strong tendency to sleep hot and/or don't have other ways to adapt your sleeping environment to compensate for a small change in your mattress (eg, you live in a hot climate with no A/C). And if you tend to be in the camp where you're often cold at night, you may even find this to be a small plus.

It's definitely a "compared to what" type question. If your other choice is a pillowtop or something thicker, then the Initiative Plush would be cooler. If your other bed is the same thickness over all or similar in design, it could be about the same. Thicker pillow top models promote better circulation and hence have a rep to sleep warmer.