Headlessness.
I too noticed that the common ground between Apple’s blockbuster announcements last week was price, size, and headlessness. But John Gruber (as always) puts it much better, and does something I can’t: he gets inside why these products are what they are, when they are.
Even if the iPod Shuffle becomes the best-selling player in the iPod line-up (and, hence, the best-selling player in the world), the word “iPod??? is already firmly established in the public consciousness as a high-quality, high-capacity player. Apple has cashed in a bit of the iPod brand value in exchange for a shot to dominate the entire digital music player spectrum, from top to bottom.