Jason,
Like all media, PPT is a tool, and tools are designed with a specific purpose and use. Using the wrong tool for a job can complicate matters. In my opinion, PPT slides should be used carefully and selectively to avoid abuse and or over use. Two components, the design of the slides, and the delivery of slide presentation are both in play, and subject to appropriate use. I think the biggest error instructors make is just because a tool is available (PPT), doesn't mean it has to dominate the presentation of course material. Like the old quip, "to a hammer, everything is a nail".
Barry Westling