Cube has long been a small favorite of mine.
The plot itself is rather interesting - being trapped in a potentially deadly cube with no idea how you got there or how to get out is a cool idea (for the viewers, anyway). The characters here are interesting in that some go through phases - at first, I think many people would be behind Leaven, but sort of get turned off by her treatment of Kazan. Quentin really tried pulling people together at the start, but toward the end, he was arguably more dangerous than the cube itself.
The acting isn't always amazing, I'll grant that, but I think for the most part, people do their jobs well. As to the conclusion, well, I can understand why some would be turned off, but given the various theories discussed in the film, I don't think anyone should really be surprised with how this movie ended. It's further expanded in Cube Zero anyway, so I'd recommend that if this movie pleased you. Hypercube is a mixed sequel, but I won't lie - I recall liking it also. Cube's a solid movie, and it's a cult classic for a reason.