I struggle with this.
Through many posts in this forum, I have tried to moderate my views. I prefer that you never have to find out how good the CS is. "Give them a chance to make it right." Well, they had a chance when they built the gun and sold it to me, didn't they? I also get the willies whenever I have a problem. Like, "All the other guns are good, only MINE had a problem, so MINE is the lemon, and even if they fix it, do I still have to worry?" kind of willies.
But I have sent a few back over the years. I bought a commemorative Para Ordnance that wouldn't feed because of a tight chamber, so I sent it back, and it was better. Then the ambidextrous safety kept wiggling apart, I sent it back, told them to just put a regular safety on, and they did. Call tags both times, no arguments. But now Para is gone, so that example isn't very helpful.
I recently bought an RIA/Armscor with a bad extractor. They had me send it back, and were very helpful and friendly....and they made it worse. So I had my local guy fix it.
I had an original Sigma that had all kinds of problems, and a local smith who was S&W authorized did all the work, no problem. But it still sucked.
I have never heard anyone say anything bad about Ruger at all.
For optics, Vortex seems to be leading the pack for CS. I hear guys who damaged scopes by torquing them too tight, Vortex gives them a new one.