Computers are never going to mimic the human brain, anymore than airplanes mimic birds. Birds and planes fly, but they do so by different methods, and so it will be when we have computers doing human tasks.
Moore's Law has several decades to go before we see cheap computers that rival the Human brain in processing power. I think it naive to expect Human level performance from any system still orders of magnitude away from Human. OTOH, we are probably getting a preview of Google 2.0
You missed the point of Watson all together.
No one in the Watson team will say that "we are replacing the brain" and knows that this is just the first step in a (very) long journey.
Rather, it opened the door on a brand new chapter in human-machine interaction and the ability of the computer to absorb and use information.
The real point in artificial intelligence is to pursue an understanding of the ultimate "computing machine": us humans. And, though we may not achieve the ultimate, we learn a lot about novel ways to use automation and radically improve our lives.
The real payoff is a better world for us humans.
Watson's use of 2880 processors and immense amount of storage to mimic just one part of what the human brain does is a testament to the design of the brain because it gives us another look at the scale of complexity needed to master the Jeopardy! problem. Watson isn't designed to drive, so it only emulates part of what we do, while requiring orders of magnitude more power to do it. Next time you read about the latest "powerful" computer, you have permission to snort milk through your nose.
Ray Kurweil offers his take in the Wall Street Journal today, riffing on his "Singularity" work.
Bottom line from his perch is machines won't take over; we'll harness them effectively. We shall see.