Good, but I don't buy that he "fell" for Ava in ONE WEEK
I think we can all say we've seen this kind of concept before: "Robot-takes-over-human..." so it's not like this kind of story is a shocking revelation. But despite that, it was a good story.
My main beef with this movie was that I didn't buy that Caleb was sufficiently won over by Ava. Maybe I missed it, but they didn't seem to have that much chemistry. Burgeoning sparks, perhaps. But in one week? Give me a break. I'm assuming the screenwriter was trying to make a parallel with the number seven being the amount of days God needed to create life on Earth, or perhaps it's just more believable that Caleb's project only lasted a week.
I don't think anyone could "fall" for—robot or human—in those conditions, in just one week. And yeah, the argument that Caleb's "preferences" were utilized to the hilt by Nathan via the search engine algorithm, etc. still doesn't render the arc believable in my eyes.
Also, this movie obviously took place in present time (the smartphone at the beginning of the film, the internet references, etc..) In this day and age, someone like Caleb should be able to see Ava's motives and predicament with a healthy dose of awareness. Unless, part of the sci-fi aspect of this story is that no one on their version of Earth has seen their fair share of "Robot-takes-over-human..." stories already! LOL. I mean, Caleb was well aware that he was testing to see if the robot could be convincingly sentient... he should know that she ISN'T, and wouldn't have been so empathetic and convinced by her to try and "overthrow" her "master", as any self-respecting, self-aware human in the twenty-first century would know already.
That said, I still enjoyed the movie. As implied, I can watch sci-fi movies with a healthy dose of suspension of disbelief. In our world, we've all seen this before. But the genre "sci-fi" itself lends itself to well, fiction.