I don't have experience with these, but I have to admit they look kind of cool with their little flap holsters, etc. A big plus would be that you can probably order one by mail without going through an FFL. The downside is that you'd then have a low powered, slow loading pistol that is difficult to shoot with any accuracy. I think I would rather have the .22 or .22mag version. I'm not too interested in black powder firearms that aren't replicas of some historic arm. Without the historical link, why deal with the hassles of black powder? But these at least look sort of like old guns (unlike the new "in line" muzzle loading hunting rifles that have NO appeal to me). I suspect that these are significantly less powerful than the rimfire versions.
That said, if someone gave me one, I'm sure I would have some fun with it.
Doug
