How have courts treated new issues raised in an appellant's reply brief?

Plaintiffs argue for the first time in their reply brief that the trial court's finding that their proposed AppleCare class was overbroad was "unsupported." Appellate courts ordinarily do not consider new issues raised for the first time in an appellant's reply brief because to do so " 'would deprive the respondent of an opportunity to counter the argument.' [Citations.]" (Reichardt v. Hoffman (1997) 52 Cal.App.4th 754, 764-765.) " '[T]he court may properly consider them as waived . . . .' " (Ibid.)