Hello,
while beeing a newbie at both Sibelius and Lilypond, and already embracing the magical freedom superiority of the latest, i recently had to make a transcript from a manuscript, and for that i used Sibelius, because i needed to produce sibelius files. This way i could enter the text by typing on a midi keyboard and not really looking at the resulting score, while looking at the original. I think it would have been slower if i had needed to input it as text. So, there may still be cases where WYSIWYG is still more convenient.
My point might be irrelevant, because i'm not an experienced user in any of those environments. Maybe there is way to do such a thing in LilyPond ? i know Frescobaldi exists and does maybe allow such a thing, but i'm on mac and don't know anything about compiling outside macports so... and i use lilypond tools, don't hink it does allow midi keyboard input.