I've installed about fifteen or so of the 4# version. Always with very good results. Only one needed a little filing on the selector for final fitting. These compare very favorably to the JP. It seems like about half of the JP's need fitting. Obviously the price is far superior.
The work Bill does is not just polishing the surfaces. He precisely grinds away from the hammer and trigger to create a shorter fitted engagement area, and then welds a bead for take up. I don't see that there is much work done at all on the actual finished parts of the fire control parts. This is good, as these parts are typically only surfaced hardened, and not much metal can be removed without breaking through to the softer core. That's why a lot of home trigger jobs wind up doubling.
I only wish he took PayPal or credit card.