You know what would be an awesome iTunes Store feature? Renting a movie, and having the option available to purchase the movie for a reduced price after you've seen it.
I often rent a movie, only to buy it afterwards at full price. Renting is an easy way to test a movie for a low price without needing to spend 15-20 euro. But if I like the movie I almost always buy it, because movies tend to disappear from the iTunes Store and I like the option to rewatch a good movie when I want to.
Since a rental costs me 5 euro in the iTunes Store and a purchase 15, movie costs me 20 euro. That is, for movies that I didn't know I would like. Movies I know in advance I'm going to like I just purchase outright.
So let's say you rent a movie, watch it, and when the movie ends, your Apple TV prompts you with the following dialog:
Thank you for renting Bladerunner, we hope you liked your movie. If you like to own this movie, you can buy it now for a reduced price.
That reduced price would be the movie's original price, reduced by the rental price.
Although I'm not sure on the financial impact on Apple's revenue this would have. Would more people be more inclined to buy after they rent (or try) the movie? Seeing something you liked offered at a reduced price could provoke an impulsive buy. Or would fewer people buy movies, and just try Them out first with a rental and only buy them if they liked them?
I see a valid argument in both practices, so I'm not sure what effect such a service would have on Apple revenue.
As for me? I'd probably end up buying more movies.