This would have been excellent had it not dwelled so much on the terrorist guy. I did find his appearance refreshing at first (a fresh and beautiful face, and a solid performance), but he's simply not lead character material. This is unlike the Sean Bean character, who gives a very fitting character and performance.
The first several moments are entrancing, and compete favorably in terms of execution (and grit) against far more expensive productions like those in the Bourne series.
The one weak spot in the movie is the beheader character. He was supposed to be menacing and heartless, but he looks more fit for a lesser movie, and the moment involving the baby was simply needless. Luckily there is no shortage of superb acting, most notably from the lady in charge, Charlotte Rampling.