Advice needed: Have/do you use tvshack.net and can you explain to me how it works?

A friend has just introduced me to tvshack.net and, whilst I find the idea very appealing, I am dubious about how it works. Is it completely legal to watch movies and tv programmes on there? Having seen some of the movies that you can view on this website it seems a bit too good to be true. I tried reading the “about us” section on the website but it didn’t really help. Can anyone explaing to me how it works and how it can provide movies to watch, some of which haven’t yet been released on DVD, free of charge? Is there any catch that I am missing here?