Radiators only radiate 20% of the heat they produce, the remaining 80% is convected up to the ceiling or escapes through a near by window. The Radfan redirects the 80% of heat that is lost via convection and blows it out into the room, giving you warmth where you need it most.
I bought a Radfan because I have a room that just doesn't heat up well and I always feel cold. Since installing it, the room definitely heats up quicker and I'm even able to turn my heating down a little too. Brilliant idea and product, would certainly recommend to others.