Hi marshmallow,
The Tempurpedic 5 lb memory foam is slower reacting than many other 5 lb memory foams and gel memory foams or gel memory foams and there are different “versions” of memory foam made by different manufacturers in the same density (see post #9 here and post #8 here) but in very general terms 4 lb memory foam will tend to be softer and faster reacting than 5 lb memory foams).
As long as you know the tradeoffs involved then you would be making an “informed” purchase which is always the most important part of good research … and if you’re happy then so am I. As you know I think highly of Novosbed and they are a good quality/value choice.
So congratulations on your new mattress … and I’m looking forward to your feedback once you complete your purchase and have had a chance to sleep on it for a bit
Phoenix