I think BH209 is geared toward the modern inlines, as some have said, and have no doubt of its efficacy for this purpose. However, I must confess that I became a BP purist about six years back and have never looked back. Smokeless powder is just a passing fad anyway, right?
As far as corrosion of the fouling of various BP subs and the real thing goes, I have not done any quantitative studies as to how fast corrosion occurs. However, it has been my qualitative experience that CajunShooter is dead on right about this. The fouling of the subs seems to be more corrosive (and at a faster rate) than good old BP. This result was surprising to me when experienced, as I figured the opposite would be true. Please understand I am not throwing cold water on the idea of progress (and BH209 is a remarkable jump ahead). There is certainly a place for it and it fills a market and works well in certain applications. It is just that the Holy Black is pretty hard to beat in alot of ways and the price is right.