I had a euroarms copy of the Rogers and Spencer and it shot well enough.
I also have two Italian Uberti "peacemakers" in 44/40 which, while needing a complete strip and polish of the internals, are pretty solid functioning pistols.
I've owned a bunch of various Italian made muzzle-loading rifles, some of which were pretty accurate. I think the pedersoli are probably the pick of the mainstream manufacturers.
There is no doubt the fit and finish cannot be compared to a quality original, but they could never afford to put that much time into it and produce a marketable product.
My favourite's however have been the English Parker Hale Enfields, I've owned all of them other than the volunteer and all have been well made and accurate.
Currently I shoot an original two band volunteer circa 1859.
Am tempted to take that one out during the roar.....

GDU