Well, I don't think netflix has anything to worry about yet from iTunes renting movies. It's a very unsatisfying experience. You only get to watch the film once and you have to finish watching it within 24 hours. That sucks. I think a business model change is in order there.
Also, without the networks putting their best serial tv up on iTunes (especially NBC), it's not as good of an experience. The best part about iTunes with an appleTV was that you could watch shows when you want within a day or two of it actually airing. That was really cool. HD would be cool, too, but I'll have to buy LOTS more drive space to support something like that, although Apple is already experimenting with it.