I just started using Montana Extreme and, so far, I am nothing short of impressed.
I use it to clean a couple of revolvers that metal foul pretty bad and the stuff seems as efficient as Sweets without the hydroscopic attitude.
My previous favourites were Sweet's & CR-10, but that may change with the advent of Extreme.
I really like JBs, but I now want to try Montana's bore paste for a comparison.