The author presents three scenarious for the radically altered future, which he calls the Heaven, Hell, and Prevail scenarios. Ray Kurzweil, the champion of the former, sees human beings as essentially becoming deities, living immortal lives (due to nanotechnology) and with brains (merged with computers) that qualitatively transcend anything humans are currently capable of.
On the other side of heaven we find hell, illustrated by Bill Joy and Francis Fukuyama (!). The idea behind the hell scenario is that the new technologies simply present too much opportunity for accidents and maliciousness and that someone at somepoint (and this only needs to happen once) will open pandora's box letting even hope escape. (Enter visions of some reproducing organical-matter consuming nanobot getting out of lab at some point and turning the entire planet into gray sludge.)
The "Prevail" scenario put forth by Jaron Lanier insists that it's impossible to see how technologies will actually be used. Unlike those who talk of technology only in terms of alienation, Lanier predicts that many innovations will actually strengthen the connections between individuals. He also points to Windows ubiquitous crashes as a reason to not worry too much about the technology getting away from us.
A good article on the book and author can be found here.
So which scenario do you subscribe to?