Josh Hartnett, He is ok but he doesn't really stir it up for me...
Sigh.... Josh Hartnett is perpetually playing these down and out sorry, soulful types that have a ruthless streak about them (Lucky Number Slevin or Sin City to name two recently). I understand that the Studios have a particular way of going about producing entertainment which by and large is determined by the currency of a star.
But I would argue that when a film is based upon more adventurous ideals such as inventive casting and a more collaborative approach within a character based story structure (i.e The Departed or 12 Angry Men for a more classic approach) as opposed to a one man ran blockbuster setup, a film transcends such hokeyness of the final showdown or overdone conventions of the guy getting the girl at the end.
So therefore why not get someone more a little more volatile or left of center to bring some vibrancy and danger to a role like say Steve Zahn or David Tennant or Sam Worthington.
Finally that being said this film looks very interesting if only because the guy directing it has chosen peculiar and distinctive subject matter; also he is a relatively new player in the Hollywood game which can be both a blessing and a curse depending on how he approaches the experience.