Just last week, I had a job with a local jazz ensemble (I'm a (french)
horn player, so this is pretty uncommon) and had to transpose a couple
parts, so since I was already punching out parts with lilypond, I copied
one piece that was so badly done in finale that I could barely read it. I
got compliments for all of the parts that I did.
Same with the jazz band I am in, no complaints about the layout done by
lilypond. Nothing was said about the chord symbols, but having the
capability of rendering them in a larger font would be good to increase the
legibility in dim light and/or when reading them over someone's shoulder.
This is another thing you find in the real books... perhaps it can be done
easily with lilypond, it isn't something I've examined in great detail yet.