I own more Kimber and S&W than everything else put togethjer.
I have never had occasion to avail myself of Kimber's CS (eight pistols owned so far), so I cannot comment on that.
My most-used pistols are my Kahr PM9 and P45. I have had one occasion to use Kahr's CS, and they exceeded my expectations. Definitely an A.
I have used Ruger's CS once, when they recalled my newly-purchased LCP over the Thanksgiving Holiday period two years ago. With a one week total time out of my hands, free magazine and hat, and shipping paid both ways...all during a holiday timeframe, I have to give them an A+.
I have used S&W's CS once (about a dozen revolvers and two pistols owned), and they were excellent. I'd give them an A.
I have used Springfield's several times (three pistols) and they were excellent, but took several tries to get it right. I'd give them an A.
I have used Kel-Tec's CS many times (4 pistols) and they sent free parts, although those parts did not generally fix the problems. I would give them an A for effort and a D for execution. I am done with K-T.
I have tried to contact Charles Daly and Colt. No response in either case. Ended up "doing it myself". I would give them an F...and I am done with Colt as well. CD goes without saying.