Just watch it (SPOILERS)

Just watch it and I must say, I really liked!

At the beginning is made obvious that Nathan is the bad guy (or is he?), Caleb and Ava the innocent subjects of his research.
The first clue that things may not be as they seem it's when Ava tests Caleb's trust by telling him not to trust Nathan. Why would she do such a thing? And why would Caleb trust her? An AI?
Since Nathan's introduction into the movie it was clear that he was shady, perhaps too clear...
Caleb was an easy target: a lone boy, who preferred to trust a beautiful girl than to trust his boss and tech mongul. Why? Not clear. Maybe his loneliness? (By the end of the movie Nathan says the real reason he chose Caleb). An ambitious person would never trust the A.I and would take sides with the rich and powerful boss,aiming to be a part of such amazing discovery. But Caleb was a romantic...
Ava was amazing. We really feel that she is hurting inside of that glass wall, we trust her although she is a robot. We don't question her decisions or her actions. We think that she was programmed to act the way she is acting. We think that she is one dimensional but by the end...boy we were wrong!
The true test was Caleb: Nathan wanted to see if Ava was capable of convincing a human on helping her to escape. Nathan KNEW Caleb would fall for Ava since she was designed to do it...what he was trying to prove, maybe, was to see how far would she go.
The ending makes people wonder why didn't she got back to rescue Caleb. I think this is simply because she felt nothing for him. She was programmed to escape and used him as a weapon to do it so. When she was free he was of no use for her. He trusted her, when he first sees her outside of the room she tells him "you stay here..". He stayed there...waiting...just to see how she wore another AI's skin and clothes to escape.
Nathan programmed her so good that her only objective was to escape even if she had to kill to do it so.
The Japanese assistant was a twist but not a good one, I suspected that she was a robot at the dancing scene...she tries to seduce Caleb and then starts dancing with Nathan, a choreographed dance? And it was ok she couldn't understand English but to not speak any word in any language? Or make any sound whatsoever?
After realizing that she was an AI, and her being an AI that could pass as a human through Caleb and by doing this, the Turing test was completed, I started wonder what was the real reason of Caleb's presence and all of his interactions with Ava.