I think the main advantage for me in ripping DVDs would be TV shows, but it would only really be handy with a bunch of metadata for each episode, so I could quickly locate an episode I just remembered. So yeah, they need the entire script of every episode to be part of the searchable data. I'm surprised TV show downloads don't have a lot more of this kind of convenience. That's one thing they could do to make downloads more appealing. Ideally, I'd be able to buy a disc, then be able to download more feature-rich versions for playback on my computer or over my network to a media streamer.
I'd really like a good place to buy high-def versions of music videos of my favorite artists. Those would be great for a jukebox-type application.
