My wife and I bought the Ultra firm  S& F (estate), and let me tell you this thing is REALLY firm. We decided to go with the topper/spring combo. The only problem is that we've had a hard time finding the right topper to soften it up a little. Right now we have a 4.1 density (I think) Isotonic Isocool 3 " memory foam. I tend to sleep very hot, but this one seems to do the trick in staying cool. My only issue is that since the winter started and our room has been cold the memory foam doesn't return to form very fast. Is this a typical problem? I have until February to return it so please let me know if anyone has suggestions.

Anyway, the S&F is close to sleeping on the floor as you can get. For those doubters of S&F, the estate series is apparently a new design. I decided to give it a shot because of the new design and there is very little foam or padding inside to go bad.

all forms of memory foam are heat sensitive and when they are cool they will not respond as quickly or return to their original shape as quickly.  I wouldn't call it a 'problem' more like an unavoidable consequence of design.  You may want to consider trying a different topper if this is a really big annoyance to you....or possibly learn to deal with the one shortcoming because it sounds like other than the slower recovery that you are comfortable with it.