I like my Leedom helmet, it has served me well. Very warm and comfortable as well.
The girl that wore the helmet below walked away, very minor concussion if anything. She was sent to a hospital to be sure, but she did not act anything like a normal concussion patient, she acted normal.
I had a major head injury in 1996 from not wearing a helmet, and I know I have whacked my skull at least twice since then easily twice as hard (after buying a helmet). Once was head first into a tree, and another head first into a 4x4 fencepost. Doubtful or not of their capacity to dissipate the energy, having one is better then nothing at all.