I have experience with drop-in barrel conversions for my G23 .40S&W. and my Sig P229 in .357. The G23 .40 has a drop-in .40 with compensator slits in the barrel. The LWD barrel is 4.9" vs. 4" std G23. I also have a 4.9" threaded drop-in barrel in 9mm to fit my G23. I don't have the offered .357 barrel. The only caveat is with the 9mm barrel installed the G23 takes a G19 magazine for the 9mm luger rounds. Both those barrels so far(3 yrs.) have performed flawlessly.
My 229 is a Sig .357 and I have the drop-in barrel in .40cal. No problems at all. They both use the same mags. Never needed any smithing done with any of these drop-in barrels.
LWD and Bar-Sto both warn against firing a new barrel before thoroughly inspecting it for any flaws. If flaws are present the barrel maybe returned postage paid by the manufacturer.