This breeding ground of error, by itself, does not cause appellate courts much concern. Thus, the biggest hurdle is not showing that a mistake was made, but that your client lost as a direct result of a particular error. Mistakes made by a judge are generally easier to attack on appeal than mistakes made by a jury. Juries decide questions of fact, and their verdict frequently involves judging the relative credibility of witnesses. Assuming there is some evidence in the record to support a jury's verdict, appellate courts won't second-guess a jury, even if the appellate judges would draw different conclusions from the same set of facts.
Errors of law made by a judge are more likely to result in a successful outcome on appeal.