I dont use it, but I heard lots of great things about NetFlix. I BELIEVE you pay a monthly fee, and have unlimited access to movies, right?
Personally I use:
www.cinemanow.com (Which just got bought out by Best Buy). There is no monthly fee, and you pay something like $3 per movie, you can download it on your computer (or if you have a TV or a blu ray player that supports it, then download directly to that), and after you download it you have 30 days to watch it,
once you start watching it you have 24 hours to finish it.
The download is real fast, and you can start watching as it's downloading, so its like streaming. Also the movies are in HD, so its cool! You can also buy movies!
It'd probably be cost effective for me to start using NetFlix instead with all the movies I watch! But sometihng about a monthly fee bugs me! LOL