The Rhapsody uses a combination of higher density 7 lb and 5 lb memory foam so it can take a little longer to break in and a new mattress will always tend to be firmer than a floor model that has already broken in. The temperature in your bedroom can also make a significant difference in the softness of a memory foam mattress.
Post #2 here about the adjustment period and memory foam mattresses that are too firm initially may also be helpful.