I bought this for my little one to avoid using piles and piles of cushions everytime we put him to play. Never expected much but this product is really good. While it doesn't protect him much when falling on his side, it does manage to reduce the impact and slow him down (because of the back part), however, it does protect the back of his head perfectly when falling on his back and that what concerns me the most. He actually enjoys falling on his back knowing that it won't hurt.
The protector is easily adjustable and most importantly doesn't bother my child while playing, which means he is comfortable wearing it. Just make sure you invest enough time adjusting it, you don't want to make it too tight or too loose.