I just started playing around with Trail Boss a few months ago and I love it. It's a great powder for beginners because it's very forgiving. I don't think you could blow up any modern gun with it even if you wanted to(but don't hold me to that
I've loaded up 38 Spcl, 357 mag, 44 mag(44 Spcl but I haven't tried those yet), 45 Colt, 454 Casull, and 460 S&W. It's a great powder for making low power plinker loads. I have found it to be quite accurate for all rounds, and it burns very clean as well. The only down side to it is that you can't make anything hotter than "wimpy" status with it. But that's what it was designed for. I guess there is one other down side to it, and that would be that it costs a bit more than other powders.