The capacitive stylus has very poor resolution, and is difficult to contrast with the part of the hand that you use for support on the screen. It would be simpler to use an optical,sound, radio or inertial add on.
Wow! Your crystal ball must be a lot better than mine. I figure early adopters several tens of thousands, most of them people that want to be seen with the latest gadget.
Then they find out that it is cumbersome to have something like this because it requires a carrier, it does definitely not fit in your pocket, which was the reason Jobs was railing against netbooks not all that long ago.
And I actually agreed with him, now it seems he disagrees with himself.
The wacom tablet computers sell in the thousands because they are a niche device, the apple tablet for now is a niche device too, until the opposite has been proven.
This is not an iphone, and the iphone is not an ipod.
Iphones and Ipods are selling as good as they do because they fit their niche (pocket devices for entertainment and connectivity) very well, this device is in a completely different class.