The plot is not Oscar-material, however, it still is worth seeing if you're up for a good spy-mystery a la John Grisham.
I enjoyed the movie immensely. The action sequences were pulse-pounding and Angelina Jolie delivers an excellent performance as Evelyn Salt. In fact, all the acting was spot-on.
It's refreshing to see a female protagonist that relies on ingenuity and technique rather than, "Oh! B00BIES! I haz them, now let me win!"
I'd definitely be willing to see a sequel. All in all, if you're looking for an exciting, well-performed movie, "Salt" would be a good bet.