I never thought I'd see a movie that actually tried to portray Hitler as a decent chap, but this one pulls it off in style. It would have been good with a "happy" ending, but maybe that's just too far-fetched for what the film was trying to do - understand the conditions in which young(ish - Hitler is already thirty) minds are so easily warped and twisted until they become monstrous.
Cusack is Max Rothman, and he makes a good job of it - I didn't realise he could do both this and "Being John Malkovich" and ace them both. Noah Taylor makes a convincing Hitler (without the trademark moustache), a small grey splotch in an otherwise colourful milieu. The director has gone to inordinate lengths to distinguish between Rothman's whirling, fresh, high society, and Hitler's miserable, colourless and ugly barrack life.
The film is expertly constructed, with every second filled with tension, and a genuine question mark over the ending. I have never watched such an unpredictable film; there are shots which play with this ambiguity throughout and the characterisation of the Jews as loyal subjects is pleasing, having seen so many films in the past where history is projected backwards, the most obvious of these being the line in "Onegin" where early nineteenth-century gentlemen "predict" the Russian revolution.
A word of warning, though - make sure you have something lighter to watch (e.g. an episode of your favourite comedy) afterwards, as you will need reassurance that the world is not all bad.