No doubt that rcbs has excellent CS when it comes to defective or broken parts as does Dillon, but Lyman is the only company that i have received poor customer service from. This of course was a couple of decades ago and things may have changed. I do admit that i have more Lyman stuff on my bench than i do rcbs though.
I have heard that Hornady leaves their customers hanging when it comes to discontinued stuff, but no personal experience with them except defective bullets which they promptly replaced. Lee precisions customer service is top notch nowadays as well. My beef with rcbs is the fact that they have lied about castings coming from China and it has nothing to do with quality.