Ruger Customer Service is said to be top notch. My only experience is having the safety conversion (transfer bar) done to an Old Model Blackhawk. In that case, I would have to agree - it was fast and they replaced a number of small items that were "buggered up" or missing. The cost of returning the gun to Ruger was not overly cheap ($45 through my local FFL / LGS), but all-in-all, it was a good experience.
My only experience with the older style "six shot" SP-101's was a number of years ago. I picked up one from a fellow, who had had it several months. He said he had never warmed up to it because it had sticky extraction on two chambers. Since it was a gun I had been looking for a while, I ended up with it.
I tried several different polishing methods to see if I could get the two chambers to extract better. I never succeeded - it came to me with two sticky chambers, and after a while, it left me with two sticky chambers. The two chambers in question would accept 22LR just fine (so they were not under-sized), but trying to extract the spent cases was a bear of a job. I finally came to the conclusion that the two chambers were probably tapered (with the bigger end in the front).
I feel sure Ruger would have fixed the problem had I returned it to them, but by that time I had decided that the SP-101 in 22LR was not for me. Too big and heavy for a 22 - the same reason I had abandoned a lovely five-screw S&W K22 years before.
All my SP-101's these days are in 357.