There's really nothing inherently great about Salt. It's nowhere near the level of greatness that any of the Bourne films reached, the laws of physics are absolutely preposterous, and Angelina Jolie isn't exactly the most memorable hero. But for some reason I enjoyed it.
I was sucked in almost instantaneously. Salt is movie that never quite lets you into the big picture until the credits role. There is always at least one question about at least one of the character's true intentions in every single scene of the movie, which is something fresh. As a result, it's exciting, and there's no real point of lag.
The only true problems that Salt experiences are the utterly ridiculous physical feats Salt undertakes. There is a scene in which she hops back and forth from roofs of cars and trucks while they speed down a freeway at 90 MPH. Another scene features her bouncing back and forth across walls as she scales an elevator shaft. Sorry, but no. At least in Jason Bourne's adventures, the things he does are somewhat plausible. When I'm taken out of a movie enough to say "oh come on", it makes the sense of danger go way down, and as a result, I have a lower investment in the character. However, this is the only true problem with Salt.
The other minor issue is something that may only bother you if you are aware of Salt's backstory. Apparently, this movie was planned as a franchise for Tom Cruise, who turned it down because he said it as too much like Mission: Impossible. I can understand why he said this. I have no problem with the fact that they turned it into a role for a woman, but I could clearly tell that most of Salt's dialogue went unchanged, and there are certain lines Jolie delivers that were clearly meant for a man to say.
Other than those issues, Salt is pretty good. It's consistently thrilling, it has a very unexpected twist, and James Newton Howard's score rocks. Angelina Jolie, while no incredible action star convincingly handles her character. She does a solid job, as do her costars, Liev Schrieber and Chiwetel Ejiofor, two people who I almost always like. Ejiofor has a fantastic range of characters he can play, and this new one is a respectable one to add to his resumé.
The ending of Salt is the best part. It sets up for a sequel/franchise very nicely, so when Salt 2 trailers start to appear, I openly admit that I'll be excited.