MIDI is about as close as one can come to a universal format

I disagree. If there's any chance of printed output being an important part of the project, MIDI is a dreadful format. Converting MIDI to ABC is very error prone and ABC (especially ABC plus) allows all sorts of other printed annotation (song lyrics for a start, but not just that) that is important for musicians and singers that MIDI can't approach. Converting ABC to MIDI, however, is straightforward and predictable.

While there are programs that will "print a score" from an ABC file, they're NOT GENERALLY PUBLISHER QUALITY scores without significant "tweaking."

The output from abcm2ps is perfectly publishable.

ABC requires specific software
So does MIDI!
It's a shame that more proprietary music scoring programs can't import ABC, though. It would be an easy feature to add.

The only reason why MIDI is popular is because so many people can't read music and also because it has applications (in fact its origin and the definition of the acronym^*) in the hardware world of synthesisers, drum machines and similar toys. It's a performance medium, not a musical notation.

Anahata

*Musical Instrument Digital Interface