My single mother often resorted to the belt to bring my brother and I in line. Until we were tall enough to reach it and hide it, that is!
We're not scarred from the experience, mentally or physically. At least I'm not.
I've spanked both our kids over the years, usually for being totally out of control. I used a belt on my step-son once for sending a pencil flying into another child's eye at school. This happened during a very difficult behavioral time with him, and I made it VERY clear that this would not be tolerated any more. It worked, and he's been great at school ever since.
The down side was that when his father learned about it, he felt I shouldn't "discipline" his son for any reason, but that it was Christy's responsibility only.
Yeah right! What world is he living in?
Feel free to comment on that one. That's probably a whole new thread topic: "Limits for the Step Parent"