Note that this idea is distinct from computers that solve complex problems on our behalf. Creating something with its own desires, ambitions, and emotions, just like us, except vastly more powerful, is there any reason to think something good will result from introducing such a thing into our environment? Does it ever go well for a species when a more intelligent species enters its niche and competes for resources?
As smart as Kurzweil is, I am always shocked that he takes for granted that such a development will be good for humanity. He scarcely gives a thought to the philosophical ramifications of a human being crossing over into a completely digital reality.
I think the question of whether super human intelligence is good for humanity is at least as important as the engineering questions about how to build one.