So, I was really pumped to watch "Lucy" because I have always liked Luc Besson and have been a fan ever since stumbling on "La Femme Nikita" way back when it was still new. Plus, in my opinion, ScarJo's stock just keeps going up and up (especially in light of her interesting turns in "Her" and "Under the Skin"). So I was willing to offer Besson a lot of latitude with "Lucy," even considering the ridiculous premise (that humans only use 10% of their cerebral capacity). But unfortunately this movie, while full of really cool visuals and some interesting ideas (not to mention lots of Morgan Freeman's reassuring baritone), was just silly.
In reality, we use most of our brain most of the time, but we maybe fully understand what is going on up there about 10% of the time. But I was willing to pretend that was not true in an effort to enjoy Besson's picture. No such luck.
I think elements of an actual good movie might have been in there somewhere, but they were obscured by the frenetic pace, the faulty, pseudo-scientific premise, and the endless exposition. Almost felt more like a metaphysical manifesto - a Besson belief statement, if you will - than an actual story.
I don't want to give a bunch of spoilers, in case you decide you want to watch it anyway, but I do want to challenge one idea that Besson introduced. He said, through the Lucy character, that humans have the mistaken impression that they are the "basic unit of measure" necessary to understand the universe, but Lucy offers her newfound insight that there is only one unit of measure that even matters - time. She makes this point by suggesting that if we watch a film of a vehicle speeding past us, and then we speed it up infinitely, eventually the car disappears. Forget for a moment the fact that her example merely exposes our finite ability to perceive the existence of the vehicle, and instead accept her premise that it is only time that gives the vehicle existence at all - that is, when we observe it at a particular place in time, we give it existence.
If we accept that shaky argument (which brings to mind quantum mechanics, kinda), rather than rendering man irrelevant, I would argue that it makes mankind essential. Without us, who does the observing? In Besson's worldview, the sole value of the universe springs from the fact that we see it.
Anyway, there are some other interesting ideas in the movie, but it is, essentially 97 minutes of nonsense and not much fun, really. Watch at your own risk.