I prefer to have the physical disc rather than downloads. It's different with music, quality isn't so important, to me anyway, I'd rather have all my MP3s on my Zen, which I can carry around with me and listen to, normally in the background while I'm doing something else.
It's going to be a good few years yet until we can get fast enough broadband to be able to watch a movie as and when we want, without having to plan ages in advance to allow for the download, and what happens if it's corrupted when you get it? You have to start all over again! ISPs are going to have to be a bit more realistic with tehir download limits too. How many Blu Ray/HD DVD size downloads are you going to be able to get, before you're limited to dial-up speed for exceeding you limit