We received a few official complaints about the translation of certain documents in which mistakes were found. You are no doubt aware of these.
As for interpretation, I could ask Mr. Ball if he has any to report. The comments I've heard since arriving here sometimes had to do with things like the interpreters' tone of voice or the fact that one interpreter was speaking louder than another. I often hear comments like that, but nothing major was brought to our attention. I believe that our interpreters are among the best in the world, because it's a very stringent exam.
Nevertheless, there are preferences. It's like audiobooks: Some people like them, but others find them rather tedious. It depends on each person's preferences.