When giving research presentations, I don't use outline slides since I am normally telling a story and believe that it is a poor use of time (hopefully I'm not instigating a debate, I just wanted to see if my logic extends to lectures)
However, I'm tempted to start including them in lectures so that students know what to expect and have an idea of the concepts being presented. I'm also thinking about the style where you periodically recall the outline to help keep the big picture.
When doing chalkboard lectures, if the answer is "yes" to the above, I would assume the same holds there. Probably a good use of time at the beginning, right?