Tightly linking hardware, software and Web services propelled Apple to a huge success with its iPod. Microsoft, meanwhile, has struggled to make its component model work on these devices and, in a telling sign, is using the Apple end-to-end model itself in its Xbox game-console business. Now, Apple is working on other projects built on the same end-to-end model as the iPod: a media-playing cellphone and a home-media hub.—In Our Post-PC Era, Apple’s Device Model Beats the PC Way