Yep, I agree, there's no doubt that watching subtitled movies is a great way to get your english level improved, specially your listening. On the other hand, lately I've been watching american series like Heroes, Prison Break, 24, smallville, among others with no subtitles at all and i'm very surprised about how good my listening is now. I definetely think this method is the best one for that purpose, although it's hard to start to practice this way if your listening isn't good from the beginning.