Day job: web development, mostly _javascript_ these days, but I've used quite a number of others over the years (including APL).
Started composing in high school in the 1890s, primarily Jazz and chamber music, with some larger works. I've been using Lilypond to produce scores for players, as well as to generate MIDI input for recordings.
My first exposure to music notation software was in college in the early 1990s, entering notes and rhythms in Finale for a professor (it was deemed a waste of time to enter the articulations and dynamics, so those were done by hand in ink).
I stuck with handwriting for many years--the only times I heard people talk about Sibelius or Finale was to complain about it, so I was never curious to re-evaluate, despite my process being pretty lame: write music on paper with pencil and ruler, then photocopy and scan it, then use photoshop to add titles and text and deal with margins/sizing/pagination.
The need to transpose parts is what convinced me to switch to Lilypond, some time around 2012. I was introduced to Lilypond through a brass band I played with that used it for its rep http://brassliberation.org/sheetmusic.php
I've been largely happy with Lilypond for small and medium-scale projects. There is of course a learning curve, but it is easy to consolidate learnings, and keep developing better and better templates and techniques. This mailing list is also wonderful.
The combination of working with larger scores, and using Lilypond for workshopping and rearrangements is my current bete noir.