We have had some feedback from our songwriters, especially those who do not play a chordal instrument (like piano or guitar) sufficiently to be able to accompany themselves as they play around with melody and lyrics.
They describe being able to try out different chord sequences, song forms and different playback styles to hear the possibilities as their song develops. Or as the song plays, they can test various lyrics for each of the verses, while having an idea of how it might sound after it has been completed.

Then export the song (iReal Pro format, audio, PDF) for their music friends or band for rehearsal or performance.