With the recent clarifications and revelations from Eiji Aonuma, we have updated our all-in-one page on The Legend of Zelda: Skyward Sword with that relevant info.
In case you missed it the first time around, one of the most intriguing new tidbits is that there will very possibly be a dungeon wherein Link loses his sword and must avoid enemies while trying to solve puzzles. Also there will be field sections which will be structured a bit more like dungeons with puzzles and bosses.
And still more intriguing is the quote from Aonuma that part of what compels Link to travel back and forth between Skyloft and Hyrule is his quest to find a “lost and valuable friend.”
You can check out these changes here or via the banner at the top of the news stories.