I really like it for a teaser poster. It's eye catching. You'd notice it across a movie theater. bonus points for no floating heads.
-Vader
What poster are you referring to regarding floating heads?
Nothing Nolan - just the nasty trend to (re)do poster art that simply shows actors' disembodied heads on some vague, maybe plot-related background. Started with DVD rental/sell through as studios wanted potential customers to see who was in the film and sell it on that appeal. Prime example would be No Country For Old Men.
I think this poster is a very good distillation of the marketing so far: the image is elegant, the concept within it is intriguing, but perhaps a little too obscure.