The negative aspect of this approach is that statistical tests on the different interface designs can't be done. The former lets one go back and forth as with normal text pages while the latter lets you jump between various elements of the document. One of the problems with a hypertext system is the homogeneity problem. On-line text always looks the same and this makes it difficult for users to recognize information and get a sense of location. This was overcome in this system by using various fonts and screen layouts.
Some people argue for homogeneity.
They say that electronic text should be consistent with printed text. But the authors rebut by stating that people read text on paper and the screen differently. They do agree, however, that the interfaces need to be consistent. Overview diagrams were used as navigational aids. Here they used two levels, although a particular application might need more or less.