"Cube" is certainly a unique movie. The brilliant, absolutely irresistible premise grabs you instantly, and the production design keeps you impressed. The first hour of this picture was thoroughly engrossing and full of surprises; I would even call it "astonishing" if the actors didn't deliver some obviously forced, unnaturally "profound" speeches, and if the director didn't try to create dramatic moments by taking the easy way out - having the characters argue with each other all the time; if they acted as a team and tried to overlook their differences, THAT would have been the REALLY original approach. Still, the movie was fast-paced and fully engrossing.
And then, about 20 minutes before the end, it begins to collapse! The mathematical calculations become IMPOSSIBLE to decipher and follow. A major character changes his behavior completely. And the ending is a real disappointment. Some people have said it's "surprising"; I think it's a total cop-out. It doesn't provide any explanations, and it doesn't provide any clues for us to try to figure it out on our own. I watched the last five minutes three times. They leave you with an intense "THAT'S IT?" feeling.
Overall, this movie is definitely worth seeing, and the acting isn't nearly as bad as most people say, but be prepared for a HIGHLY unsatisfying ending. 6/10.