Very nice, the plot held together, the characters had some character, and the visuals where well done. A rather smart play on questioning reality, with some clever twists.
It didn't quite have the wow factor of seeing The Matrix for the first time, but it had more character development and a more complex plot. This is a clever movie with some action, not an action movie with a clever premise. It is a movie you need to pay attention to understand though, there are several levels to this onion, and they move back and forth a lot.
They kept their fictional technology pretty internally consistent, and it makes a little of sense, which greatly helps this sort of movie. There was one huge gaping hole with gravity, but other then that it works.
The ending is a bit predictable, but it fits the movie very well.
Jay