I let this sit and "puff up" for about 12 hours before putting it on our bed. It has straps on the corners that hold it in place (even on a larger mattress like our 14"), which I really like. Stops it from sliding around. 
Not all of the squares seemed to have the same amount of fill. Several are almost completely empty of fill, which is disappointing. It does make a difference in comfort, although not anywhere what I expected from a 4", but that may be due to the poor fill. 
I struggle with getting very hot during the night, I didn't get hot with this topper on our bed. 

If it had been filled properly, I probably would give it a higher rating.  - J's wife.