I'm a Netflix customer. For $20 a month, I have three of their DVDs sitting at home at any given time. (Current DVDs: March of the Penguins, Flight of the Conchords (season 1, disc 1), and Firefly (disc 1).) Would the addition of movie rentals to iTunes be enough for me to give up Netflix? I've been mulling it over.
Netflix has given me a few things that I like. The major reason that I signed up for it in the first place is that I can keep a DVD for pretty much as long as I want to. The DVD arrives in my mailbox, and I watch it when I feel like watching it. There have been many times when I walked into a traditional movie rental place, walked out with a film, didn't watch it that night like I had intended to, and ended up returning it unwatched because I never had enough time or didn't feel lie that film.
Another feature that I've come to like is the queue. My queue has 128 items in it right now. When someone recommends something to me, I look it up, and if it seems interesting, I toss it in the queue. Every once in awhile, I go through the queue and bump something up so that I can watch it sooner. This means that I don't have to remember movie recommendations anymore, Netflix manages all of that for me. I love that feature.
I've found that their suggestion feature is pretty good. They seem to get it right. It's not 100% (no, I really don't want to watch Balls of Fury), but it's good enough that I scroll through their list to see what is there, and add a few ratings if I see that they've suggested something that I've already watched.
The social aspects of Netflix have also kept me as a customer. I like checking out the movies that my Netflix friends have watched to see where our tastes match up and diverge. I like seeing what the other residents of Mountain View like (Helvetica and The Sopranos right now).
I don't go to the Netflix site that often -- maybe once every couple of weeks. But every time I'm there, I spend at least a few minutes, and my Netflix queue grows. However iTunes handles rentals, it will have to be more attractive than Netflix is to me now.