This distinction from the post below, that media can either be collapsed (Content, Container, and Interface as a single piece, as a book) or expanded (each separated, as in a DVD, remote, and screen) explains a bit about why the Touch interface is so visceral. The iPad feels different from other devices when you use it, and one of the reasons that I believe it does is that it collapses what have been expanded media types. With the iPad (and to a lesser degree, the iPhone, Android devices, Microsoft Surface, etc) you directly interact with the media and information you are working with. When you watch a video on the iPad, the Content, Container, and Interface are as-a-piece, and you interact with the video by touching the video itself.
This has a lot to do with the revolutionary feel of these new touch devices…and I think it explains why previous attempts at things like Tablet PCs may have failed.