See it if you want, but you won't be any worse off if you skip it. The premise is great, but a great premise does not a great movie make. And this movie is more Bruckheimer than great. It has moments of good comedy and cleverness, but they are doused by expensive action sequences. How are these assassination agencies so undercover when they routinely blow up large structures and engage in destructive freeway auto-fights?
If you're living, you know that Pitt and Jolie play a married couple who don't know the other's a contract killer. Why do you know this? The ads have told you, again and again, before each movie you've seen the past three months. This torpedoes some of the delight of the film's first 20 minutes. We know their secret, so we could've started 20 minutes in.
Pitt/Jolie are fine entertainers but finer specimens.
I'd like to think what Mr. & Mrs. Smith would've been like with Brian De Palma directing.