Here are some things I use BIAB for:

1. Playing the melody of a tune on my tenor, in unison with lead instrument and rhythm, to keep my intonation and time honest.

2. Listening to the chords of a tune and then soloing over them.

3. Generating an endless stream of sight-reading material in many styles and keys with the Soloist.

4. Adding new tunes to my book and printing lead sheets in C, Bb, and Eb.

5. Having fun, as decreed by Peter Gannon.

I bought Band in a Box to use as a practice tool, and that's still its primary role in my musical life. Though Real Drums and Real Bass make for an amazingly realistic accompaniment, the most important capabilities for me are still those fundamentals having to do with accompaniment (including easy transposition and tempo change), generation of melodies and solos, variety of styles, and notation. I hope PG will not abandon further development of those capabilities of this wonderful program in favor of pretty horn sounds (which are way cool, but I still want to be the best-sounding horn in the room when I practice).