The secret of Apple Design
Brunner estimates that today Apple spends 15 to 20 percent of its industrial-design time on concept–far more than most other computer companies–and the rest on implementation. He says that Apple rides herd on manufacturers, sending design-team members to factories for weeks at a time to see what can be done and to push manufacturers to find new solutions. If the designers see a true innovation, they can integrate it into their designs and check the quality of execution at the point of manufacture.
Nice article on design at Apple by Technology Review magazine.