Buy it, with all the Real Drums and Real Tracks you can afford the next time a special pops around. Or buy the Audiophile edition.

I am a songwriter and used BIAB for drafting songs and then even developing very good drafts. The piano, bass, and drums on both of the songs "Dancing With You" and "For Our Childrens Children" were directly from BIAB:
http://www.myspace.com/tallpaulandfriends

You can't beat it for a quick way to change tempo, change keys, change style, add instrumentalists... you name it. And RealTracks is the icing on the cake. If you have a great synth, you can even get great sounds via MIDI. For example, the piano in For Our Childrens Children is MIDI then sent into my external Roland synth.

Paul