The movie is a revenge/espionage story focusing around a strong female lead - in concept its not unlike Salt (which I reviewed here), but this movie works on an entirely different level.
Here's why you should see it. 1) If you like high action/compelling character stories (like the Bourne trilogy), it will be right up your alley. 2) The lead, Saoirse Ronin (who I've liked in pretty much everything I've seen her in) is really really good in this movie, seriously, I cannot stress enough how good she is in this film, and 3) Cate Blanchett makes one hell of a villain.
I don't want to get any further into the plot than the trailer does, as this type of movie works best with only a little knowledge going in. I figured I was in for some fun action when I went into the theatre, I was blown away by how good this movie was as I left.