We heard about the Tummy Tub on a TV show on the Baby Channel. Apparently the shape is supposed to comfort baby by putting them into the fetal position. We found easy to use, firstly you only have to support the head. It really calms Ollie and brings up any wind he might have.
It is really great value for money at about £20 and the only problem we had were the screams of annoyance when we take him out if it!