Hypertext is clearly useful for certain forms of information retrieval (especially task-oriented forms such as on-line documentation) and for some kinds of fiction. However, I have some serious reservations about what the effects could be if hypertext were to move to a central rather than a peripheral position in our textual world, taking over our ways of knowing in the same way that print (according to theories of transformative technology) created a new worldview out of the old oral world.
These concerns cluster around analogies between reading hypertext and watching television. There is much to criticise in this analogy, of course. Hypertext is still text, though as hypermedia it can contain long passages of visual and aural media (leading Michael Joyce to call it "the revenge of text on television"). It therefore may retain many of the important properties of knowledge formation that we attribute to print and tend to deny to television (despite Marshall McLuhan's dissenting voice.) In particular it may escape being totally co-opted by the center-to-margin mass entertainment configuration that has made educational television almost a contradiction in terms.
But the analogy sticks in terms of the pattern of consumption. Like television, the structure of hypertext encourages a rapid movement from item to item that could discourage reflective engagement with the medium. I do not find this a happy thought.