Computers are clearly different and complementary to our own brains. We most definitely don't know how to replace our brains with better hardware, but having some kind of implant that would allow me to maintain a perfect calendar in my head instead of on my phone or computer would be really helpful, as would being able to do complex arithmetic a the speed of thought instead of the speed of typing equations into a calculator/Mathmatica/etc. It's not about replacing anything we already have with something better, it's adding new tightly integrated features.
