I watched it this past weekend. I liked it even more when it was over and I was having to explain why the ending was exactly what it should've been to my GF.
I agree that Emily Blunt was good for the part and her character needed in this movie and did\was exactly what they wanted her to do\be. She's supposed to be the whiny detractor amongst the group of "get it done" badasses. The movie was drawing a contrast, once you get that, you realize why she was good for the part and the character was necessary. The whole point of the movie was that they needed a Federal Agency for cover, she and her partner were chosen for the gig, and they didn't quite lay down like the SAD guys wanted\expected them to. What pissed me off about her and her partner's characters was how naive and ignorant they both were. I mean, you're head of a task force yourself and you work for the FBI and you are dumbfounded at first and secondarily shocked that, in the war on drugs, there's CIA shenanigans afoot? Really? Do either of you bozos watch CNN or have heard of the INTERNET?
I totally knew Benecio's character would kill the wife and kids. Knew it right when that scene started. I understood his character's motivation was and what his capabilities were from the get go. The only part I didn't like was the monochrome "night vision" scene with them in the tunnel. Felt more like watching someone play COD than a movie, but it didn't take up enough time to really piss me off. I am excited for the sequel (it's, apparently, in the works) that's going to follow him and shape his character.