What can I say, this is an excellent film - subtle and
sophisticated. It is a perfect sequel to the first, and like a perfect sequel actually makes the first better to. The special effects aren't that expensive but their not bad and the hyperspace thing is pretty convincing. The best thing about this film though is that it has that grasp of subtle realities that puts it up there with the early Hellraiser films. This achieves exactly what Event Horizon tries and utterly fails to do.
The people in this film come face to face with the reality of hyperspace, a reality that most of us cannot accept, where they meet multiple realities and realities that conflict. At the end you still don't know the purpose of the Cube (other than to torture people), and its obvious that the first cube in the first film can be seen as a prototype for the second in the second. (OK I am into hyperspace and ftl geometry which makes me kind of prejudiced, and I'm not sure you'll even get the punch line or much of the film without the ability to grasp HS (hyperspace)).
Set in the same reality as the first Cube, in a world surrounded by an utterly merciless military that killls without thinking. A film that never needs to tell you everything or lead you by the hand, where the author leaves you some genuine sense of mystery.
My only warning is I don't know how many times you can repeat watch it, a problem with Donnie Darko to! Saying that this is definitely in my top ten films for the last ten years.