I think styluses are for geeks only. Using handwriting recognition and gestures is like writing on paper, only it's not really. It's also like using your desktop PC, but not really. Geeks like us can learn these new conventions and have fun coping with a stylus. To most people it's a terrible pain in the *ss.
Taking up a pen tablet also involves taking up the stylus. That's 100% more overhead than something like the iPad. A paper reference book can be looked at, browsed, indexed, flipped through just by putting your hands on it. Install software to allow that on a pen tablet, and you still have to pick up that stylus in addition to going to the tablet.
In short, it's more immediate. It's immediate enough to reach a mainstream audience. Pen tablets were not.
I mean it IS cheap. The data plan IS cheap.
I had never heard of a tablet pc; until, I was browsing craigslist for a cheap Wacom solution last month. I've heard of an iPad and its not even in stores yet. It will probably be half a decade before I stop hearing about the iPad.
Perhaps we should give it a chance.
I'm afraid I haven't been paying attention: is there a brief, cogent argument for why the iPad will do this whereas the Tablet PC form factor did not?