Spoiler free review:

Starring Scarlett Johansson, Lucy is a movie about unlocking the full potential of the human brain, instead of just the 10% we are led to believe.  Before I say anything further, let's just address the elephant in the room.  We do NOT use only 10% of our brain.  We use all our brain, to varying amounts, throughout the day.  http://www.snopes.com/science/stats/10percent.asp

So let's just assume there is some kind of untapped potential available.  Indeed, intelligence is not determined by the size of the brain, but by the volume density of the brain and its neural pathways.  That's why smaller animals can be smarter than bigger animals with larger brains.  If we imagine Lucy's brain is generating new cells and pathways at an exponential rate, the movie becomes a "little" more believable.

I say "little" because the amazing abilities she gains are pretty unbelievable.  I *could* believe she gains a greater understanding of everything, which allows her to manipulate people and objects in ways unfathomable to the normal person.  Imagine if someone handed an Australopithecus a lighter.  That'd blow its mind!

I liked that as Lucy became more powerful, she lost her humanity.  Just like Doctor Manhattan from The Watchmen, she cares less about the little things (except clothing... unfortunately she keeps caring about that).

The Good: Scarlett Johansson
The Bad: The 10% brain capacity myth
The Ugly: All the action is in the trailer.  Rest of the time is just a lot of detached staring.

Spoilers from this point onwards....

Speaking of Australopithecus, the film starts with another Lucy.  We are introduced to a CGI "missing link" Lucy splashing in some primeval waters.  I thought it a nice callback to another "evolutionary" Lucy, but I don't think it quite fits.  Modern Lucy doesn't become the next evolutionary step for humanity.  https://en.wikipedia.org/wiki/Lucy_%28Australopithecus%29

She becomes a God.

Seriously, she is everywhere and everywhen.  She has total control over all matter.  She has seen (and supposedly understood) what birthed the universe, and likely its purpose for being.  She may even have created it (although the film doesn't specifically show this, but there's no reason future Lucy couldn't decide it was necessary).

My opinion is the movie went too far with the capabilities of super-intelligence.  The whole "mind-over-matter" spin should have been avoided.  They should've stopped at giving her ninja abilities (by being able to think ahead at quicksilver speeds) and what greater understanding and predicting could do.  You want her to "see" cell phone transmissions?  Have her build something that makes no sense to us.  More action, more empathy, more danger.

Her total control over matter and her own cells obviously means she can enhance her vision, muscles, everything to whatever she needs whenever she needs it.  We only care (somewhat) about the people around Lucy by the end of the movie, and it's obvious she doesn't care about them.  They aren't developed enough to actually connect with, so the movie kind of falls flat.

It was enjoyable, but not what I was hoping for.  Rotten Tomatoes gives it 60%.  I think that's fair.

I can get on board with her losing her humanity (or at least her emotions) as the film goes on, but I thought that the way it was acted, she just became more of a mouth-breather with a perplexed look on her face.  Aside from that, I thought that the development of the other characters and her relationship with them left a lot to be desired (I'm thinking mostly of the Interpol cop here - she basically used him for his car, but they tried to make it seem like it was far more than that later in the film, but I just didn't feel it).