So we all know that the 24 hour limit sucks. That (along with the fact that you can only get HD content if you have an Apple TV, what could otherwise be the killer feature for me) certainly prevents me from me from even considering it as an option beyond something to keep in the back of my head for last resort instant gratification.
Netflix, by contrast is of course quite happy to let you keep DVDs for as long as you like. As a subscription outfit, they just make more and more money off of you. But plenty of people would certainly prefer to pay per rental and herein lies the problem as renting on a long enough time frame becomes indistinguishable from buying.
The solution: Instead of putting an arbitrary cutoff time after hitting play, there should be a virtual check back in. You’d a allowed to have, say, 10 movies checked out at a time, paying for the rental when you download them and keeping them as long as you like, but you wouldn’t be allowed to download the 11th until you “check in” one of the 10, rendering it unplayable. Certainly this would introduce some more security holes and would set an upper limit on how many movies you could take with you on a trip if you don’t want to access the internet from the road, but it would prevent wholesale abuse. On the whole I think it would work much better for most people.