IMHO, S&W's Customer Service is the best in the business.
A friend had a 340 (bought used) that had small (pepper-flake sized) bits of metal disappearing from the front side of the cylinder. Sent it in to S&W and it was back in five days with a new cylinder--no recurrence of the problem since.
I bought a 396 (bought used) that a previous owner had damaged the finish somehow. I sent it back and asked for an estimate on refinishing. They refinished and returned it in under a week, no questions asked, no charge.
From what I've read, neither of these experiences is unusual, except if you compare them to other companies.
For what it's worth, I have also had to return pistols to Kahr, Springfield and Para. All did well, but none as well as S&W.
I have also had other "name brand" pistols that I should returned but the manufacturer showed no inclination to accept them (even though they were purchased new), so I sold them at a loss instead. Instead of naming names, I will say that if you read my posts, you'll figure it out...and if you don't, my experiences are far from unique...