Firstly, I've never suffered from this problem, so my opinion is based on others' experiences.
I think that having the dealer replace the sub-harness is a good thing to do, it will prevent the most common problem with these ground connectors.
Obviously from this thread title there are several other connectors that can give problems, but less often than S4. I would suggest a trawl through this whole thread will give you a better idea of where you want to go.
In my opinion, if you are suffering issues that can be tied to these, removing the connectors and soldering the ends of the wires together will effect a cure, but not easy as some have very little free wire, some are difficult to access.
Some people suggest running an extra ground wire round them and back to the battery negative, my personal opinion is that this is unnecessary, the loom behaves perfectly well apart from corrosion in the connectors, eliminate this and you eliminate the problems.