If like me you grew up in fifties, this was one of many films, classed grade 'B' which in many cases had class 'A' feel for style and intelligience, if not the big stars, and was run a LOT.
Present generation, with some exceptions would probably greet it with a yawn, or just turn off. They are weened on over the top action and gore; and NOT IN COLOR! No way! But a good film of it's genre and generation at a good price.

I've got mixed feelings on this movie. On one thing, it was a complete movie. There were decent characters and development, plot, conflict, special effects that did not involve tinfoil or gorilla suits, and some decent Sci to back up the Fi. However, something in this movie feels empty. It's generally bleary, with a depressing pall that's not fully lifted by the no-place-like-home ending. The movie doesn't have much action, or fantastic creatures, or natural wonders. Like the underground world it explores, it is dark, cold, and barren.