This makes me think that his is really a quiet thrust back into general computing, from a platform, hardware and software ecosystem that's been very successful and is wholly owned and controlled by Apple.
The current Mac ecosystem is basically no different, or just a variation on, the PC open platform. Jobs has stated many times in the past that he prefers to "control the end-to-end user experience" which is code for "prefers to control the margins on Apple products, from hardware to software".
Everything in the iPhone ecosystem allows Apple to control the end to end margins retrievable from the consumer. The Mac ecosystem lost this message a long time ago and this seems to me like a soft-shoe effort to turn the Apple consumer onto a new computing platform that's on the Steve Jobs "margin controlled" message.
It also cleanly gets the moved away from the Wintel style computing and back into proprietary and incompatible land. Within two years, people will be using these things for general computing, with mice and keyboards and webcams and all kinds of specialized docks and iPad 2nd monitors and such. Within 5 years they'll offer a complete out of the box computer running in this constrained ecosystem and traditional Macs will be relegated to some type of "Pro" offering targeting writers and artists.
Already it's principle release feature is the presence of 140k apps, ready to roll with it that you can purchase only from the Apple controlled online store. And there's discussion on porting more traditional productivity apps (iWorks) to the platform.
Effectively, this puts the iPod/Phone/Pad derivative products into direct competition with Apple's own products, which already have plenty of competition from traditional Wintel boxes, Netbooks of all varieties, other tablets, the upcoming Chrome OS machines, and Android computing platforms. But because it's so tightly controlled the intersection in the primary computing ecosystem is minimal.