yep, this is a stone cold classic. there are about 4 different versions that i am aware of, all with different run times and in some cases different music.
but it is an all time great science fiction film, just dont expect wonderous effects or indeed great acting (if judging in a modern sense that is). its more for a film buff or people who love sci-fi films and want to see where they all sprung from. its #109 all time on imdb, which means as much or as little as you want it judging from some of the rubbish that exists on the imdb list.
having said that though, how many other 1927 silent films are still lauded today? if you like films then my advice is to go for it, its only £4 after all...