Not the OC, but for me what I lost was the identification of a set of clear, discrete points (with references) that I initially thought contributed to the essay/document.

Sometimes I discarded the nuggets as better ones came along. Sometimes the thesis subtly changed as I gathered these nuggets. Sometimes the layout changed drastically as I shuffled my index cards. All before I even committed to my essay structure.

Not OP, but having some similar experience I'd say being more grueling, it forced the writer to accumulate experience faster. I'd add that besides the management of the aforementioned snippets that could be copied in at same point, part of the snippet-level editing, that nowadays goes on the computer, before it was just done mentally.