I agree Bob, the quality of free BIAB files is all over the place. I'd love to see just ONE collection of BIAB files that was put together by someone with discerning ears whose goal was to isolate "the best of the best"

I'd gladly pay money for this collection, because it would save me the time required to sift through thousands of unsorted files.

If somebody out there has lots of time (and good taste), here's an income generating opportunity for you. Given the huge number of BIAB users worldwide, such a collection could become a real cash cow. If you removed the melodies, you could probably sell the collection of chord progressions on ebay.