I saw this elsewhere... I just about jumped out of my skin when I saw that poor cat fall out of the tree! I imagine the owner had to calm one scared cat afterwards.
Cats are less likely than humans to be injured by falls because their body weight is lower than a human's, resulting in less momentum to be expended in the collision between cat and ground. Still, there is enough momentum to make injury quite possible, even likely, in falls of this distance. Being able to twist around to land on their feet (at least some of the time) may diffuse additional energy before it can injure the cat; the cat's legs bend as it strikes the ground, partially supporting the cat's weight. It works about the same as a crumple zone on a car.
Oh, yes... you can tell I'm a physics major. Still, I wouldn't wish such frightening occurrences on any cat, even if they *were* all guaranteed to be as lucky as this one (which they certainly are not!).