Just ran into this thread, & even though it's a year & 1/2 old, I'd like to comment:

I LOVE iReal Pro, & I really can't imagine doing w/o it. Even though I'm now a retired music teacher/church musician, I use it (& have used it) in myriad ways:

+ when writing original music, to keep track of the chord changes, form, & to try out diff. rhythm patterns & tempi.

+ to write up a background track for a song at church, when I couldn't find a background track available to purchase. I've even written up a quick track (if it was a simple song) in the morning before church & used it in that morning's service.

+ for more involved arrangements, I've used iReal to lay out the basics of the arrangement, & exported the track as a Midi file, & then imported the Midi file into Logic Pro on my Mac.

+ for one pretty involved piece I wrote (a jazz piece w/ four horn parts & rhythm section), I used iReal to create the rhythm section parts. Interestingly, the bass & piano parts sounded fine in Logic imported as Midi files (using Midi instr. sounds in Logic), but the drum parts sounded much better exported out of iReal as audio files. Prob. has something to do w/ the Midi "mapping" of the drums.

+ another fun thing I've done is that if I like the drum part in one rhythm style, but I like the keyboard part in a different style, I'll just export Midi files of a song using the two diff. rhythm styles, import them into Logic, & just keep what I like & delete what I don't want. Just gotta make sure the tempo is the same for both.

+ when my friend that I play jazz with & I use