I bought two of these for my two children for our journey on a long haul flight recently. The cushions keep their shape no problem at all. When my children actually used them whilst they were asleep, the cushions didn't fully support their neck as I hoped they would. I still found that with my 4 year old, his head would still drop to the side and he would end up in rather uncomfortable looking positions!! I tried re-arranging the cushion position, the incline of the chair, but to no avail.
To summarise, the cushioned offer some support for the majority of the time. It was better than having nothing at all.