I've never dealt with it.

I want to hear what it's like when you have to?

eta

For the record i don't have any issues with any of the current S&W pistols i own odly enough i've never had an issue with a s&w product (i've owned a bunch).

Kicking around buying a few new guns and wanted to know what it's like when you do get a bad one.........

World class, call them, they will take care of you.

I had them refinish a model 27-2.

Got it back and the finish was not as I would have expected.

Called them and they said send it back.

They refinished it no questions asked.  It arrived in great condition.

I was not impressed. I sent in a m&p 9 that wouldn't shoot good groups.Having owned 4 other m&p's, I knew something was really messed  up with this barrel. I sent the pistol in, and received it back about 2 weeks later with nothing done to it.I immediately  called thinking that they misunderstood the problem. The s&w rep pulled up my file, and said  , the pistol was fired, and found to be in spec. I ,of course  asked , what is your spec, because this thing shoots terrible. I laughed out loud , when they told me 4" at 7 yards.
All a smith and wesson m&p needs to achieve is 4" groups at 7 yards.Thats 8" at 14 yards, 12" at 21 yards.I am not shitting you.I would imagine any pistol in the planet could pass that test.What a joke.I sold the gun, and when I do my pistol classes for women now, I no longer recommend s&w products.

Extractor in my 25+ year old 4516 broke.  (Just for kicks, I tried to shoot it, and it still worked.) 
I thought about getting a local gunsmith to replace it, but decided to let S&W do it.  I figured they would certainly know what they were doing. 

Called S&W, was very nice, and told them that I was a big S&W fan (true).  They wouldn't provide a quote without examining the pistol (sounded reasonable). 
They emailed me a Work Order and a shipping label.  It was addressed to something like "SW Industries". 
They returned it fixed in about a week.  Fixed under their lifetime warranty.  They even paid shipping both ways.  Didn't cost me one dime. 

For the record i don't have any issues with any of the current S&W pistols i own odly enough i've never had an issue with a s&w product (i've owned a bunch).

Kicking around buying a few new guns and wanted to know what it's like when you do get a bad one.........

I have called them a few times for little stuff, like frame plugs for M&Ps, mag floorplates, etc.  plus my newest 9mm Shield had to go back for barrel replacement. I have no complaints, everybody I spoke with was very helpful.
I just now sent in the paper on two Shield rebates, so we`ll see how long that takes.

In my experience I have had a shield magazine spring bend beyond repair. I called them and in about 5 business days I had a new spring in my mail box.

Only needed them once.  The L frame recall on a gun I bought used.  Painless transaction, took about a month to get the pistol back.  I suspect they run these in batches.

My new 351c went back and came back better but still has issues. I am being lazy about sending it back again. They have been quick about sending me parts for guns in the past.

I bought a used Shield 45 that had an extremely weak spring in one mag.  Called them and had a replacement mag in about a week.  Offered to pay, but they swapped it out for free.

I was happy.

They've been good for me. I haven't needed customer service from them very many times.

I had a bodyguard that I had an issue with, (I think it just didn't like to ignite super hard primers). Anyway they did everything they could to figure it out. I'm pretty sure it was related to a particular ammo though.