Most the experts have a positive view but lets focus on the ones we can skew into a fear of Skynet along with celebrities. Woz being one of the better opinions.
Domain specific knowledge is needed to make educated guesses or at least informed assessments of the current threat level. Currently, AI is not at all intelligent; with in a specific narrow domain the AI can do as well as or better than a human. Big deal. So can a horse or a car - they are superior within their specialized domain. We are nowhere near a general artificial intelligence; we are making slow progress on simulations of natural intelligence which might prove interesting and possibly quite disturbing someday; but if you can simulate a natural brain's intelligence that isn't artificial is it?
Back on topic, AI is only applied intelligence within extremely narrow domains. A thermostat is an artificial intelligence; within it's domain/context.
Talk of Gigahertz is grossly over simplified. Biological brains are massively parallel and the interactions going on involve quantum mechanics (although may not be necessary for operation-- it likely will be a huge problem for simulators.) The gigahertz is hardly important when you have a network mesh that is MUCH larger than the neurons within it...
The REAL issues are how jobs can be simplified so an average or slow human can perform the job. Those jobs are beginning to be feasible for customized AI systems to perform and replace the human employees. Furthermore, just as kids can solve protein folding problems by playing a game, an AI can be augmented by human brain power in ways that simplify the job greatly. Your 6 year old child could be putting you out of work with their video game playing. The real cyborgs to think about will be AI attaching human intelligence. Like a surgery robot which does most the work with the surgeon assisting multiple bots at the same time... reducing the number of surgeons required (think of all the prep work etc that could be automated...)