I've been writing ethnographic field notes for about 15 years. I had a couple of phases of trying to do this electronically, but the notes from each of those 3 month experiments are for the most part now lost or at least difficult to access - proprietary formats, failed backups, accidental deletions, you name it. Whereas the paper notebooks are sitting on my bookshelf beside my desk. For one project I chopped the spine off the notebook and dropped the pages into a bulk scanner before perfect-binding the notebook back together again, but the resulting physical notebook is a bit more delicate than I'd like. But I do like having an electronic version, both for backup and so I have a copy available when I'm away from my bookshelf. So these days I photocopy each notebook and drop the photocopies through the scanner (and more recently I've been able to have a student or an intern do it, but for a task I only needed to do every three-six months it was never that onerous to begin with), storing both the photocopy and a copy of the pdf offsite. I've played with various indexing schemes over the years, from leaving the last dozen pages blank and writing a single-line description of the contents of each page as I filled it (2002-03-21: key informant interview, ER doctor, hospital xxx), through to embedding metadata on relevant pages of the pdf to make it searchable (my handwriting is way way too bad for ocr to have any utility). But the 'write the index on the last few pages of the notebook as you go' method has been the simplest and most robust, and it rarely takes long to find anything, even with 30 or so notebooks on my bookshelf. And picking up an old notebook every few months and just reading or skimming through it is often a worthwhile exercise, reminding you of ideas and streams of thought and research context in ways that simply searching for something you already know is in there never can.
As an additional benefit, I've always found making notes in a notebook to be less intrusive in meetings or interviews than typing or using a stylus on a tablet (although changing social norms may make the latter less intrusive eventually), and the act of writing to be less intrusive to my own thought processes than typing (maybe just because no red squiggly lines appear under my notes as I type, or text reflowing, drawing the eye as it does so), but that might just be me, or I might just be showing my age.