Ok so you want to download movies quickly but also with the guarantee that the files are legitimate. Here's the answer BitTorrent. If you read the link you'll see that BitTorrent is by far the best network to download files larger then 100 MB. Gnutella the network LimeWire runs on is the best for small files such as individual songs. However if you want to download movies, the complete seasons or even the complete series of tv shows, or download complete albums by your favorite artist BitTorrent is the way to go. There are many programs that run on the BitTorrent network. The original BitTorrent client invented by Bram Cohen the inventor of BitTorrent is just a basic client. There are better more efficient clients out there such as Azureus, BitComet, and my favorite µTorrent. In short Azureus runs on everthing and is written in Java like LimeWire, contains numerous plugins but is a system resource hog. BitComet is written in C++ and runs on windows and is less of a resource hog but is banned from many private trackers due to a bug in the code of an older version. Last but not least µTorrent is written in C++ and is the lightest BitTorrent client on the market requiring no installation and less then 170 KB of hard drive space but is not open source. I suggest you read up on these programs and others that I didn't mention and decide for yourself which program you want to use. You may even want to download a few and test them out to see which one works best for you.

Good Luck!