I like the service. I have found nothing suitable to replace it, yet. It is a good value.
Will cheap DVDs threaten Netflix? Netflix saves me from having to buy any DVDs. I see no point in buying, no matter how cheap they are, because I seldom watch a movie more than once or twice. I have hundreds of VHS tapes I never watch.
Will pay-per-view replace Netflix? That is unlikely for someone like me. I am unwilling to pay the extra money for digital cable or a special tuner in order to get pay-per-view, even if they had all the movies in the world. I hear the quality isn't very good yet, either. (Sidebar: I hate being a slave to the cable industry. Years ago, they promised us a plethora of a la carte channels with the advent of digital cable. The greedy muggers lied. I hate being forced to accept twenty channels filled with foul-mouthed prostitutes, just so I can watch Farscape or Animal Cops.)
Will I ever download movies? I don't have a big enough hard drive, video card, bandwidth or computer screen for downloading and watching movies. so it wouldn't work for me unless they made a cheap appliance, like Tivo, that I could attach to my TV. Why should I pay a thousand dollars for a new computer, just so I can watch movies?
I am considered by some to be an "early adopter", so Netflix is no problem for me. However, I have many friends and co-workers who hardly ever turn on their PC at home (or don't even have one), seldom go on the Internet or check email, but they watch two or three DVDs or movies on premium cable per week. These people are great potential Netflix customers, because they can understand and use the rent-by-mail model without having to learn any new technology.
Whatever movie-download or cable pay-per-view service moves in, in order to replace brick-and-mortar stores or rent-by-mail, will have to have technology that's really intuitive and invisible to the consumer.
Until they solve the hardware, technology, and bandwidth problems, Netflix's rent-by-mail service is the best way for me and my friends to get a wide selection of movies really cheaply and easily, without having to be slaves to Tivo, Bellsouth, or Time-Warner cable.