Whoa whoa whoa... let's step back some of IBM's marketing BS just a notch there: If you read what IBM actually wrote, they claim that their magical chip consumes 70 milliwatts running at what they refer to as "biological realtime". Now... WTF does "biological realtime" mean? Well, using a relatively sane definition of the firing rates of neurons in the human brain, the neurons fire at anything between ~ 1 Hz up to 200 Hz depending on the neuron type and level of brain activity (see:
http://neuroblog.stanford.edu/?p=4541 ).
So... 70 Milliwatts at maybe (optimistically) 200 Hz?? Not too shabby, but nothing miraculous either especially if IBM is being smart enough to use power gating so those "5.4 Billion" transistors look more like the few hundred million transistors in your smartphone running at any one moment in time... oh and those transistors are running at an intentionally crippled clock rate.