To state the obvious, the down topper is only about 3" high and it will compress. The product still is borderline useful for me as I use a very old, very hard cotton batting futon, so almost anything would help. I also wanted something natural rather than a memory foam just because....
I can't see how this topper would add much value to a normal mattress, the other review notwithstanding, however I do agree the topper fit my futon exactly, is well finished (no quills) and does add a feeling of luxury for the first 60 or 90 seconds until it compresses "down". I don't have much luck fluffing it up by patting or by rotating or by flipping it. It compresses again just as quickly. It was borderline not to return it for me, and given the cost I would not recommend it to someone who had any mattress or futon save the very hardest kind.
The Facts: We have a queen size bed. I bought the queen size down-top feather bed. It fits the bed perfectly, edge-to-edge. We have a great mattress. The down feather bed makes it about a million times more comfy. This is a very luxurious item and worth every penny. No quills to poke me. I bought the cover to go over it and it fits perfectly, too. Both of these items are great and the feather bed is a wonderful addition to our lives (really!).