I just remembered one little piece of technology in Snow Leopard that could be telling:
EASY PDF TEXT SELECTION
"Mac OS X Snow Leopard applies sophisticated artificial intelligence algorithms to fix the problem. It analyzes the layout of each page in the PDF to identify columns of text."
I remember thinking at the time that this tech is pretty crazy for something that would be handy, but not exactly killer... Apple describes it as "an enhancement that exemplifies the pursuit of perfection..." which even sort of acknowledges that they have gone to extraordinary lengths for something that people probably weren't exactly DYING for.
What I'm thinking though is that it's not a stretch to imagine this technology being used to identify columns of text in a PDF NEWSPAPER or PDF MAGAZINE? Think about how mobile safari works right now - double tap on a block of text to zoom in on that text. I assume it can do that on the web because these pages are marked up in HTML, so Safari knows a bit more about them. This AI technology could do the same for PDF documents where there's no markup
Apple then opens up the "Book Store" or "Print Store" to change the game again. They could partner with media companies to deliver electronic versions of newspapers to these devices (think Kindle / NYT). They partner with publishing companies to deliver electronic magazines and books. Think of how awesome a design / photography mag would be if you could touch a photo in a layout about a famous designer which launches a slideshow of their work.
I see that as a game changer. People certainly still like to read newspapers, magazines, books in the age of digital. A device like this could be killer for those people. Media / Publishing companies probably wouldn't be a tough sell since they could keep the ads intact in the layouts as well.
I also see it having a VERY high resolution screen - already the iPhone is rather nice to read text on, but higher resolution again would be approaching the comfort of e-ink devices.