I haven't used it yet but have some. The main reason it was brought out is because of the new shooters trying to cut cost and either were under charging or over charging. With Trail Boss you can't double charge and blow the gun up.
A black powder shooter was telling me about Trail Boss and the man I bought the gun from told me to use it. I will one day have just one powder to use in all my 6 guns and rifles if the Trail boss works out as good as they are telling me.