I've done it three times, two on deer and one on a bull elk, and wasn't happy with any of the results. The elk was hit right between the eyes, but that placement actually misses the brain. I watched him dance around backwards and sideways until I shot him through the lungs. One deer I shot was hit right where his horn touches the hair on his head, so in essence, I just clipped off the horn. I was on the other side of a canyon when I shot him, so I just watched him for a while. He was out for about five minutes, then slowly got up and walked off. I had to find him and re-shoot him. Another time, a deer trotted off and stopped with his head just over a bunch of bushes staring back at us, so I tried for head. The shot was low and hit him just under the chin. Good neck shot, but not what I was trying for.
Since those experiences, I vowed to take only the most perfect, close up headshots, and if I feel funny about it, I'm going to pass. Bill