I just spoke to my boss who owns a used 330ci convertable (I think). He bought it used not from a dealership. He has taken it to Fields a number of times for warranty related repairs and service and says he has been very happy with them. They always give him a loaner (renatl car). Once they did slip up and forgot to send a rim out for repair, he called them on it and they were very apologetic and covered the $300 bill to have it repaired for his inconvenience.
That sounds like pretty good service.