I thought this was an interesting point from the presentation. I think it's easy to forget that the students work all day and can get bored even with fairly interesting material. Anything you can do to wake them up and refocus them on the material is useful. I do use slides when I feel like I have to, but one of the best pieces of advice I ever got from a dean was to ditch my slides in a knowledge-heavy class. I used the white board, handouts for key technical items, and demonstrations whenever possible. Made a big difference in the excitement level of the classroom and hopefully improved learning.