I have been using it for years — you get he DVD, hang onto it as long as you like, then send it back at your leisure. The price determines how many you hang onto at any given moment.
And more and more of the movies are available for online streaming, and those are unlimited.
Netflix has about 95% of all the films and TV Series I have been interested in. Some of the old Silent Movies are just not available, but in general it is all there.
My wife was looking for Mission impossible I couldn't find it on the net. I notice netflix has it.