Fascinating. Just like how I found Equilibrium's Gun-Kata revolutionary a few years back, Parkour is awe-inspiring. Such agile, light, fluid movements.
The two main actors are true star athletes. They ARE their own stuntmen and master of martial arts. And Parkour actually exists; it's not some kind of make-believe in the world of cinema. The style is refreshing compared to the overused wirework or CGI. Most of the stunts are dangerously and breathtakingly real.
If you're an action/martial arts fan, this is a MUST-SEE. Don't go for the plots or the acting; the constant chases and duels alone are worth the admission price and then some. Surprisingly, BOTH the critics and the general public are in agreement on this one!