Better than I thought, not as good as it could have been.

Rating: 4/10 (25 July 2014)

I couldn't expect very much from a movie based on the myth that humans only used a small percentage of their brains. This notion, harped upon very much by nuns making the point that their students were lazy, was debunked sometime in the pre-mythbusters era. So now it doesn't even make good pseudo-science for a fiction plot.
It's rather startling that Lucy director-writer Luc Besson apparently never got that memo, and its more startling that nobody bothered to correct him before he made a whole movie based on the idea.
If the scientific basis is poor, the plot concept is solid and absorbing: an American woman is captured overseas by a crime syndicate and then is used as an unwilling mule-vessel for some new street drug. She's captured and tortured by a rival gang (I presume, anyway, see below.) While being "worked over" the drug packet in her breaks open. This might not be such a spoiler, because it's all in the trailer.
Oddly enough, even considering it's based on nonsense, I enjoyed Lucy. Scarlett Johansson does a good job as the title character. Of course, you can't find many people who look better on the big screen than Johansson. The problem is, after the first five scenes, she's not really a character anymore. She's become more like a force of nature--a monster really. Usually a friendly one, but still not one anybody can reason with or oppose.
That does get to another flaw in the film. You aren't given a lot of time to get to like the main character before she becomes a monster, and she seemed likable. At about 90 minutes, the film felt too rushed. In fact, it almost becomes incoherent at one point. They seem to have over-edited and left out a scene where Lucy is captured and tortured by a rival gang. (I presumed that's what happened. The trailer seemed as clear on this point than the film did, which is to say not very.) The movie has a lot of gun play, of which Lucy is generally not involved because if she's there, she wins. It sports an international cast, including, Chinese, French and Italian. If I'm not mistaken, it probably has a radically different cut in China and Europe than it does in the US, which is hardly an excuse for leaving key scenes out.
Another problem with purported "underused brain" notion is that Besson inter-cuts scenes of a Professor Norman (Morgan Freeman) giving a lecture on that basis. The lecture parts are dull as any lecture, even with Freeman giving it, and are made duller by the fact that it's all nonsense. Nothing Norman says even touches on the real world.
Besson compounds his error by showing us the running percentage of Lucy's brain usage. In short, you're not allowed to forget the stupidity of the "underused brain" myth and just go with the fact that Lucy is becoming mentally more supercharged.
Besson tries to make a deep philosophical point about the nature of existence and time, even within all the shooting and action. He might have succeeded in his philosophical point, except the movie has no credibility due to its basic stupid brain hypothesis. It's the old paradox of science fiction: how does a writer of average intelligence or less write characters of extreme intelligence? Lucy crashes into this paradox like a mack truck into a concrete pylon.
But, if you ignore that, and just accept that she's becoming more and more superhuman, Lucy's not a bad movie.
I would rate it a 5. Despite the lectures, the film kept my interest, and I wanted to see what happened to Lucy. It loses another point, though, due to its major editing error. I don't care how many markets they edit for, in this day and age, there's no excuse for that.