You should note that Apple MacBook Pro users need to buy the Apple-branded EmPower plug... this is because the MacBook Pro is (somewhat of) a power hog and will blow out an EmPower port using a generic adapter. The Apple-branded adapter triggers the MBP to stop charging the battery (power is used for operation only), allowing the computer to operate without tripping the breaker.
(I suspect Apple could probably have enabled this in software so that users could still use a generic EmPower adapter... but then again, maybe not. At the moment, the Apple-branded adapter is the only option. But let's not start any comments about Apple or the Mac, please... this post is simply for informational purposes relevant to the thread.)