I have been using BIAB for several years, mainly with the melodica. It would be the rare dude who understands and is able to use all, or even a high percentage of its functions. It's like learning to play an instrument. I currently have UltraPlusPak 2016 with the hard drive. The most delightful thing about BIAB is the Real Tracks, tracks laid down for chord progressions, etc. by professional musicians -- real instruments. So you can be accompanied by Ron Carter on bass, for example, and Kenny Barron on piano. You only get a sampling of the available Real Tracks with the basic versions and have to pay $500-600 to get them all (for example in the UltraPlusPak), but you can start with the basic version and then upgrade.
garywj is right that BIAB can do wonders for your timing. You can work on timing with the melody track (midi) and then mute the melody track (or any instrument tracks you wish within a particular style. Working with just one accompaniment track can also help your timing -- obviously with the drum and/or bass track, but also with, say, another track for that style (piano, guitar, whatever) that requires you to keep the rhythm straight rather than just following a rhythm track.
I have figured out how to use the (minimal) ukulele tracks and to show the uke chords on the lead sheet, though I have trouble with the latter muting parts of other instrument tracks. There's also a problem mentioned in another thread for playing with a low G string. The uke chords are shown for re-entrant tuning. But I'm a beginner on the ukulele, trying to play Jazz, and the available BIAB Jazz files and lead sheets for BIAB show no mercy for ukulele players.
I love BIAB and use it every day. In actuality, it's a terrific bargain at $500. It requires a steep price in time and energy as well as in dollars, but the time is spent learning and making music.