normally i'll take any opportunity to bash MS but i personally like the pen idea.
it says right in the article that its a multi-touch screen, right? so how can anyone reasonably assume the pen is the only method for input? what would the point of a mult-touch screen be if you could only use the pen? Hmmmm?
I would say it depends on age.
For "texting" I think the world record is like 30 words per minute.
At the speed 1/2 the kids I see text I would say they beat that easy

.
Common complaint of iphone here is u can not get the "speed" for texting on the touch screen.
When the first typewriter came out, people had a hard time adapting to "thinking on keys".
I would say for the immediate market (until people stop using paper and pens) it is a good idea.