that you can make presentations that are self running and that MS offers a free PPT viewer that anyone can download and view these presentations.
It is obvious that PowerPoint is more vivid and practical than PDF for presentations. But there is a problem that sometimes we can not use PPT for slideshares because not any computer get MS PowerPoint or other OS don't support PPT format such as Linux. So we have to use PDF for replacement? Have you feel any unconvenient?