This thread brings up the major issue with downloadable content that drives me crazy. Compression sucks. The bandwidth required to download uncompressed files is not readily available. Until the next big revolution in internet connectivity occurs, hi-definition downloadable movies are only for people with great connections or those people who don't mind compressed a/v.
However, when the bandwidth is there, the movie and tv industry is in for a major shake up similar to the music industry. (MP3s also drive me crazy. Paying full price for a compressed song blows.)