Mentioning the Newton makes me think of how Microsoft still seems obsessed with handwriting/pen interfaces. This may be a generational thing. There seems to be an assumption that the average person finds writing with a pen the most natural way to record information. But I bet there are a lot of us now who spend more time typing on a keyboard than writing with a pen. I found myself surprised, for example, when the user hand-wrote a URL in the browser app to go to a page. Hand-writing a URL is a pretty foreign experience, except in those rare cases when I need to remember a URL and I'm away from a computer (and I can't remember the last time I actually did that).
Your comment also got me Googling for the Simpson's clip that was pretty much the Newton's tombstone. But I found the video introducing the Newton at the bottom of this page more interesting:
http://technabob.com/blog/2007/07/20/classic-apple-moment-ne...
One interesting thing is that it is clear that the Newton was struggling to find a way to move data around before the dawn of the world wide web. You can print! Or fax! At least, you can the next time you are physically next to a device. Or you can "beam" something who happens to be in close proximity. Er, if they also have a Newton.
The fact that literally half of the intro video is devoted to getting the handwriting recognition to work correctly, though, is certainly ominous. It indicates that the hand-writing interface was not as intuitive as they had hoped.
Which brings us back to Microsoft and pens. I wonder if the vision for tablet computing was born out of Gates and his generation's familiarity with hand writing and inherently assuming that the average person is more comfortable with it than keyboards, and not updating those assumptions for the current generation who spend far more time updating their Facebook status on a keyboard than taking notes in class (assuming they don't use a laptop for that, too).