If apple think their iPhone success shows that people like closed systems, they are kidding themselves. Phones have never really been open (thanks to the carriers), so the iPhone was actually one of the more open phones out there. But once they start competing with actual computers, it is going to be very different.
The Newton, just like any other tablet computer had a niche, vertical applications.
And it failed in that niche because of choices set in stone by the Apple team that developed it.
It wasn't open enough.
So, forward 21 years and we're in 2010, where we see a sequel to the Newton, running a proprietary OS on hardware that has been closed to the point where you can't even attach a USB stick.
I'm sure that lots more of these will be sold than there ever were sold of the Newton, but I doubt it will tap the potential of this form factor. For that it needs to be much more open and hackable.
This is just another remote terminal attached to the web, and more importantly for Apple, to itunes.
There is nothing wrong with remote web terminals, but as long as they are computers you should allow access to all that power, locking it and making it hard to put software on it is limiting, not enabling.