I'll say one thing, Kurzweil is optimistic.
Kurzweil is on the Army Science Advisory Board, has testified before Congress on the subject of nanotechnology, and sees considerable potential in the science to solve significant global problems such as poverty, disease, and climate change, viz. Nanotech Could Give Global Warming a Big Chill (July, 2006).
He predicts nanobots will be used to maintain the human body and to extend the human lifespan.
Kurzweil has stressed the extreme potential dangers of nanotechnology, but argues that in practice, progress cannot be stopped, and any attempt to do so will retard the progress of defensive and beneficial technologies more than the malevolent ones, increasing the danger.
He says that the proper place of regulation is to make sure progress proceeds safely and quickly. He applies this reasoning to biotechnology, artificial intelligence, and technology in general.