Tangentially related: a high-regarded literary editor from my country told me that he seems to notice more text-level details when he is reading somebody's draft on an e-reader, as compared to working with a paper printout. I think I have had a similar experience myself.
+1 also on Gaiman's thoughts. I have done a lot of writing (professional level journalism, closet-level fiction). I almost always write a better first draft longhand -- probably because writing by hand is so much slower, you'll end up with a much more concise sentence.
From another perspective, I recently finished "The Kindly Ones" by Jonathan Littell. 900+ pages of Kafka-style wall of text -- but I often just couldn't put the book down. So stream of consciousness still seems to work from a reader's perspective, too; maybe computers do give some "oomph" to a writer who prefers this style, the kind of feverish way of writing. That said, "The Kindly Ones" is definitely a unique, remarkable, even incredible book; part of its power surely lays in the fact that Littell reportedly did some 10 years of research prior to writing it.
There have also been prolific and influential writers in the past who composed their drafts in pen shorthand. Iirc, in Europe, Astrid Lindgren was one (and I believe she was actually trained as a touch typist).