I assumed this was a low-budget student-made film, based on the number of ratings and reviews, so I was not expecting anything good to come out of it. There were certainly moments that broke my suspension of disbelief; moments in plot that made no sense, ADR that sounded off, and brief moments of unbelievable acting, but overall, it was better than I expected.
In contrast, the main cast was phenomenal, both in performance, and in recognition. Imagine my surprise to see that an international director doing his very first feature-length film roped in three world-class actors.
In all honesty, it was the acting that held the entire thing together - as you may expect from a film set almost entirely in an elevator.
It was definitely slow to get going, though. It wasn't until the half-way mark that the plot actually got interesting. Occasionally things would happen that offered no value to the story line, and until the forty minute mark, a lot of it felt like filler, like the movie wasn't going to be long enough, so more scenes were added.
Nothing was more annoying than thinking something interesting was going to happen, only to realise that nothing was happening at all. I began to get bored after the opening sequence.
That being said, if you can endure the first act, you may be pleasantly surprised by the second, as things begin to pick up the pace, and the characters really begin to develop and take on their own stories.
In the end, I wasn't impressed by the actual plot, and its conclusion. It was an interesting idea, to be sure, but it made for a rather dull conclusion, when it was revealed what it's all about.
Basically, I was pleasantly surprised by the film, but only because I expected a no-budget indie film.