One thing I've wondered about, are different fonts and colors possible with DVD subtitles? Would be cool if they could somehow match the style of text used in the movie itself.
The studios never seem to do much with subtitles beyond white, yellow, and kind of blocky. (And it's really annoying when they inexplicably replace burned in subs with them too.) Closed captions on an old 1980's tv set have more visual appeal. ;)