I just bought for my Kindle: Baron, Dennis (2009) A Better Pencil: Readers, Writers, and the Digital Revolution. Oxford: Oxford University Press. For a review, see American Scientist. I'll let you know what I think in the new year.
From the review: "I have to add that my own view of the computer as a writing instrument has always been that it’s not so much a better pencil as a better eraser, allowing me to fix my mistakes and change my mind incessantly, without ever rubbing a hole in the page." First reaction: I think the computer is both "a better pencil" and "a better eraser." The two functions are equally important. But the delete function on the computer adds something important, namely the ability to store what is erased.
When I write the final copy of an essay with the word processor, I always create two files, one called "name of essay.rtf" and another one called "scraps for name of essay.rtf." The scraps sometimes come in handy in another context. A versioning system is overkill for my purposes. Furthermore, for the earlier drafts ConnectedText provides automatic versioning, anyway.