I have trouble with the convention of foreigners speaking English with foreign accents so as to indicate that they're really speaking a foreign language—a serious disability when watching American films—and it didn't help that each of the main cast members had a different idea of what constitutes an appropriate accent.

See my second reply to ap_aelfwine; I think very few of the cast were adopting accents. But I can see how it would still throw you out of the illusion to hear a conversation conducted by three ostensible Germans, none of whom speak with the same accent at all.