Other than the fact that the prisoners didn't seem to have much of an ethnic mix the screenplay seemed to be authentic enough and it stands up well in comparison with other prison movies.
Its main attraction is that it is highly original but it loses some of its impact by spending too much time on the love interest – quite a bit of which had nothing to do with science fiction.
Unusually Demi struggles a bit in this. Having the Costner and Hurt "characters" on screen together is a bit clumsy at times but I suppose it is better than having two Costners.
It has some delightful touches of offbeat humour sprinkled here and there in an interesting screenplay. It is performed by an interesting mix of a cast which includes the great character actor Peter Vaughan.