These opinions contain a lively (and interesting) debate amongst the members of the panel regarding both the general issue of prosecutorial vouching and the particular predelication towards this practice by members of the of United States Attorney's Office in Nevada. They're definitely worth a read. The majority opinion contains a pretty compelling -- and disturbing -- recitation of the prosecutor's argument here, alongside a history of this particular prosecutor that suggests pervasive continuing abuse. The dissent (by Judge Trott) articulates (particularly in the final section) a fairly personal -- and expansive -- contrary analysis, and one that insinuates both that the Ninth Circuit is uniquely out of control with respect to vouching issues and simultaneously that the U.S. Attorney's Office in Nevada is somewhat out of control for continuing its antics.
Both points of view are cogently argued here. They're valuable additions to the literature.