@reillypascal @paul I use it for everything. Composition, engraving of historical scores. In recent releases the markup language also got way more expressive and "semantic" (\fine instead of \bar "|.", etc.) so its even more fun.
Just a random note on your screenshots, `\relative c'` I find mind-boggling, I am firmly in the `\fixed c'` camp (So I prefer to choose the "primary" octave the voice works in and then use , and ' to move to the neighbouring octaves. \relative c' just always surpises me and is instable if you do edits within a melodic line.