INC Magazine has an article this month about the uses and perils of powerpoint by Adam Hanft.
While acknowledging its usefulness as a tool (don't kill the messenger), it also states:
"Objections to PowerPoint ring numbingly true to anyone who's been exposed to its obsessive-compulsive organizational structure and truncated syntax: PowerPoint is a radical oversimplifier. It artificially marches the audience to a predetermined conclusion. It chills discussion."
From a PR perspective, we acknowledge the usefulness of PPT to keep one's thoughts organized. However, it should only ever serve as a framework for a conversation. We advise our clients to keep a presentation as close to 15 slides as possible, and to include one slide that could be used to tell the whole story.
Furthermore, we also remind clients that PPTs can be a bear to upload and download given their sheer file size. You should have a low-res version that can be used for email.