We have never changed tables, but in our many cruises there were a couple of times when we probably should have. Our best tablemates were a couple of years ago when we were the only Americans at a table for ten. It was great discussing how the various countries govern and how at the end of the day we all had the same hopes and worries.
I guess we could take about anything except someone who constantly whines and complains about perceived problems with minor things. I think we all know someone who always seems to have a major problem on almost every vacation. That, for sure, would push me over the edge.