Cruise is a rogue secret agent who takes Cameron Diaz with him on his adventures, when she becomes entangled in his "keep the MacGuffin away from the bad guys" mission. Diaz is great in these roles, being funny and mostly incompetent while preserving her self-respect.
The movie is full of taut, gripping, mildly innovative action sequences. Early scenes take place in Boston, and I found them convincing. I could not say where every scene was supposed to take place in the Hub, but it sure felt like Boston. The remainder of the movie takes place in Europe, (including a motorcycle chase amongst the Spanish bull run), which improves its overseas marketability.
The only aspect of the movie which does not work is the so-called "romantic" parts. I think we're supposed to believe that Cameron Diaz and Tom Cruise's characters feel some kind of romantic, or at least sexual feelings for each other. The problem is, Tom Cruise's acting has become so stunted, that he exudes all the sexual energy of a washing machine or blender. He looks deeply into Diaz' eyes, and they stand close to each other, so I assume there's supposed to be lust of some kind occuring. There's even a squirm-inducing scene where we learn that Cruise changed Diaz out of her clothes and into a bikini while she was unconscious. He awkwardly excuses himself by pointing out that "I can reassemble a machine gun with my eyes closed, I can get you into a bikini without looking." Well, that's troubling for two reasons. One, isn't stripping a woman naked with your eyes closed still, erm, sexy? And second, Cruise is so non-sexual these days, I didn't believe for a second that he would actually enjoy it. As I pointed out in my review of Valkyrie last year, Cruise "has devolved to the point where the only emotion he's capable of is single-minded determined certainty." He's a technically perfect action hero, I could watch him run and jump all day, but when he tries to put on the lovey-dovey eyes, he's as convincing as a puppy.
By the end of the movie, they ride off into the sunset together, but it felt more like a brother and sister on a road trip than anything romantic.
It's easy to get distracted by the "faux-mance", but the rest of the movie was a fun night out. My grade = B-minus.