I have used BiaB for many years for practicing playing leads through a song's chord changes, like jazz minus one. It is real nice for that. But I only use the drums and bass, leaving the guitar, piano, and strings turned off.
Sometimes I will use it to make a lead sheet for some song, chords only.
Band in A Box is pretty usable as a drum arranger. I used to a setup song in BiaB, then export the midi drums only. Pickup the midi drums in Sonar, and tweak them, using a decent drum synth. But now I use Jamstix for this purpose.
I have used it for song arranging, but only in unusual situations. Once I recorded My Funny Valentine using the BiaB African beat. It was unusual enough that I got away with it. For the most part, it is a little too cheesy for my taste.
I really with they had a windows interface. I have brought this up, and they insist they need to keep their legacy interface so old customers will stay happy.
They pickup the phone and are responsive to calls.