It's a 90 minute Twilight Zone episode

Rating: 8/10 (20 July 1999)

And if you like TZ, that's all well and good. There's no real explanation for the goings-on (only a vague X-Files type conspiracy theory), but not a lot of TZ episodes stood up to rational analysis either.
You do have to wonder who built this thing, since other than the Cube itself, nothing seems particularly "futuristic".
There are a few questionable premises. The implication is that the characters all have skills that contribute to their escape. Well, first of all the doctor doesn't. Secondly...this implies this is a deliberate test that particular characters with particular skills were all placed together. But then we're led to believe the whole thing is random. So...which is it?
There are also some minor nits, like who cleans up all of the many (presumably) bodies that have gone before? Why does no one clean up Rennes' body, so that it is left behind as a plot point?
Some of the math seemed a little shaky to me. And I wasn't too impressed with the math whiz. She has to look at a three-digit even number for a couple of second to figure out it isn't prime. Ummm, hon, if it ends in an even number, it can't be prime. If it ends in a '5', it can't be prime either, but she actually has to stare at it for a couple of seconds to figure this out??
The characters themselves, however, are interesting enough, given that we're not seeing them in the best possible light. Maurice de Wint, an underrated Canadian actor, probably gives the best overall performance. His switchover to savagery is a little too abrupt (one second he's saving the doc, the next he drops her) for my tastes. And the writers can't resist giving him a Jason-like "return from the dead" sequence.
The other characters are an interesting lot. I wasn't impressed with deBoer (but her "talents" on DS9 often escaped me as well), but David Hewlett is perfect.
Overall, Cube is not your typical film, so going into it expecting a happy ending is probably not a good idea. It does make you think, though, although its most important issues (Kazam's final escape) are not spoken.