I find that BIAB is extremely valuable to me for PRACTICE. Nowhere else can I really get into the chord structure (and melody lines, solos, individual parts) as easily, to play along on my MIDI keyboard. Those who have not seen the latest 2007 version should take a peek. Take a REAL peek at the new function that will pull chords and structure from MP3, WAV and related files.
For example, there are a number of "jazz riffs", intros, ending, etc. stock in the program. Call one up, play it copule of times, slow it down -- read the notation sheets and play whatever parts you wish.
Truly a marvelous program. I did not really appreciate it until I decided I needed much practice with my left hand (too much arranger time). I am sold.