All of the features you mention require a broadband connection.
It downloads images and such for the discovery bar. The little show summaries and thumbnails that appear on the right side of the 'now playing' list look like they're also fetched on demand.Netflix and Youtube are not unexpected, but broadband being necessary for the HD menu is a bit of a surprise.
It's good if you don't have high speed internet at home. Yes, there ARE places that still only have access to dial-up. Only problem is these areas are rural, so the daily call is likely to be a toll call.The Premiere does not include a modem inside, so to use a phone line, you have to go to tivo.com/store and order the phone line USB dongle. This item is kind of pointless as functions are quite limited.