Steve,
I've considered a stop loss for some time. It's recommended by most trading publications. If one is trading with a lot of leverage, it makes sense. It could be the difference between success and failure.
But I use little leverage. If I have conviction that I'm investing in great businesses or sound economic interests, then I want to be exploiting lower prices, not retreating from them.
Besides, if you let an automatic stop loss take you out, when do you know to go back in?