I've no idea why this film has had such poor reviews from some viewers or has turned out to be so polarising but it would appear to be one of those features which you either spectacularly love or loath.
I have to say I absolutely loved it. The plot is simple enough but while parallels can be drawn with the Bourne films' identity crisis motif it is a very different feature. Jason Bourne/David Webb was an adult who was engineered into some sort of super soldier by participating in a strange government behaviourist-psychological mind control experiment. Hanna is younger, ignorant of being a legacy of a similar project and living in the wilderness, there is no need to recover memories or resolve a crisis of identity. Instead the driving force in leaving the wilderness is a desire to experience life more fully and directly than what can be told from the sources available at hand to her and her mentor/watcher.
There are so many excellent themes in this film which are only partically touched upon due to time, pace and requirement to progress the plot onwards to its conclusion. They remain none the less excellent. For instance the interactions between Hanna as a socially isolated and consequently socially maladapted person with the precocious child of bohemian liberal parents. The scene where she is in awe of electric light and then overwhelmed by all the disturbing noise created by the TV, telephone, kettle and other mod cons in concert.
The villains are convincely evil, each one in their own way exemplifies as certain kind of sado-masochistic character, from the agency woman who brushes her teeth until they bleed, to the skin heads and malignantly perverse tracker killer (who with his retro track suit appearence and skin head cohorts has a sort of seventies or eighties villainy quality about him) who are employed to trail Hanna.
The acting is done well, the soundtrack and accompaniment is fantastic also, the Chemical Brothers really have provided the perfect sound for the dystopic near future the characters inhabit.
If you liked the Bourne films I would recommend this, I would recommend it as perhaps better infact than the Bourne movies (although the Bourne books were better than their film adaptations).