I have used Band-In-A-Box alot. I work with a songwriter that does everything in BIAB and then gives me a disk to load into my machine to add guitars, etc. In fact, a song I co-wrote with this guy was placed in a movie and other than the vocals and an electric guitar solo the entire production was BIAB. Keep in mind BIAB is basically a sequence program to drive MIDI sound modules.
That being said some BIAB styles are decent and some are as already indicated "cheesy". It depends alot on the style of music. Some of the jazz styles, blues shuffle, country, etc are decent. But BIAB won't cut it for rock or pop.
In most styles the piano parts are decent and the bass lines are functional, but the "guitar" parts are weak and the drums can be hit and miss (basic grooves aren't bad but the fills can suck)
You can go in and edit many parts (how deep into the programs you choose to get is a matter of getting to know the software), but you can do some serious tweaking of the sequence patterns if you choose.
I will be honest, for my own projects, I will start in band in the box just to get a basic song arrangement together, then I start to replace most of BIAB with actual performance (via MIDI). Sometimes I keep the BIAB piano parts or bass line, but everything else gets replaced.
Depending on how MIDI savvy you are vs. using samples & loops - you may find that something like ACID (basically a Sony loop based platform) may work better for your needs. Like BIAB, ACID has many style "disks" that you can buy - but the ACID disks are much more expensive than the BIAB disks.