It's a rule that doesn't generate many opinions, so you might find this one interesting. In Adams v. Ford Motor Co., the Third Circuit explores the text of the rule, analyzes the due process rights of the accused lawyer, and then reverses the magistrate's finding that the lawyer had violated 3.5. [edited]
UPDATE: As Dan Abrams points out in the comments, the Third Circuit had to deal with a standing issue. Sometimes courts will say something negative about an attorney's behavior and the attorney has no standing to challenge the dicta.