Hello Dick .. as mainly fiddle player into old time country, irish trad and cajun trad i always find that general programs using midi are just suitable for a guide track.
With BIAB's current on board realtrack thing you're one step ahead, and sometimes a really useful thing pops out. Especially with the help & soul of a real musician captured there. It might not always be exactly what you need, but when you don't want to spend tons of time and dough with musicians and studios, BIAB is number one.
In final folk music recordings i sometimes used bluegrass banjo tracks, sometimes even slowed down and pitched, or a mandolin rhythm. Even used a bodhran pitched and stretched in a different musical context. Or a pedal steel as i don't know a live player around here. As for irish stuff and bluegrass within BIAB i wouldn't always call the found styles there as such, and the generated music just that, but that's personal. As for Irish music the recorded bouzouki and bodhran in BIAB are not my thing really; f.i. i once had the luck to play with Johnny McDonagh in ireland, and he's simply the most versatile player around: Youtube link:
De Dannan ([video:youtube]
http://youtu.be/tGrA_8_t4to[/video])
You'll need time to find the right thing for your piece of music, especially if you want the result in a certain context. BIAB is a very diverse and general tool that sounds great. IMO most interesting for musicians into jazz, pop, rock, especially country, and bossa etc. Electric guitar work recorded there nearly perfect. Thus maybe not so much for acoustic folkies like me. Like there's no nice trad cajun grooving style in BIAB.
As tool for composing for film, video or songwriting i found BIAB a great weapon when you need to do a fast dirty and cheap job, or to get an idea for an arrangement in a lot of possible styles. Don't forget it's great leadsheet printing facilities: i found a lot of use for that when you have rehearsals and studio work interacting with live musicians. Or for teaching irish fiddle as sometimes in my case.
PS - Realtracks maybe due errors and the way the system works IMO are less suitable when you play with timing settings within a song, like an occasional 5/4 or 2/4 bar in a 4/4 piece of music. If you intent to publish your music on CD etc, the audiophile .WAV realtracks are a lot better than the cheaper .WMA ones. I think PGmusic still has the x-mas offer for the whole caboose at a very fair price until half January, you might be cheaper off buying the whole caboose in one packet right now. - F