There was quite a discussion a couple of months ago on a black powder cartridge rifle forum about Ballistol and there was much of the same reaction as I see here. One of the shooters there is some sort of a whiz-bang scientist so he did some testing of various cleaning and rust preventive products. Ballistol rated very low as a rust preventive, although it was a pretty good cleaning solvent. I was surprised that it didn't do a lot better than it did as a preventive.
Any way, it seemed in the final analysis they recommended it as a good cleaning solvent but don't depend on it as a good rust preventive, especially for long term storage. It was noted by those folks that many of the people who were completely satisfied using it as a rust preventive lived and shot mostly in the high plains areas of the country where humidity levels average a lot lower than in the Eastern and Southern parts of the country.
I have never used it myself on firearms (I do want to try it), but we did use it in a machine shop I worked in as a kid.
Regards, Dave