I play a lot of jazz, so I use BIAB as a jazz combo backing track. I set it for three choruses. On the first, I play melody, on the second I solo/improvise, and on the third I do a bit of each. Great learning tool and great fun!
I play mostly jazz standards which you can download from several sources, the best being http://tech.groups.yahoo.com/group/Band-in-a-Box/. Just join the group and access two long lists of songs. They also have some country, blues and pop.
You can then pick/create your own style (use Real Tracks), tempo, key, etc.
It's like playing along with a professional jazz combo.
My dogs are big fans.
Cheers!

Cheers! -Alastair