I take neck shots all the time. My father takes them too. We have never lost a deer we shot in the neck. They have all fallen right away. Between the two of us we have close to 50 years experience, and numerous kills. We both shoot a .270 with super X bullets (they used to be superX, now i think they're the silver tips or whatever).

Contrary to popular belief, you don't have to sever the spinal cord to take them down right away. If you're a little low, it won't actually sever the spinal cord, but it will rip the neck out. When taking neck shots, if you aim for a little bit above the middle of the neck, you'll be fine. Now, if you can't hit the bottom of a Coke can at 100 yards consistantly, then i wouldnt take a neck shot. I dont ALWAYS take neck shots, if its near dark or raining, or if something just doesn't seem right, i take the shoulder shot. But on a nice sunny clear day, and that deer is standing broadside, I go for the neck. If you do break the neck, then it sure makes it easy to cut the head off though.

Anyways, thats my experience.