There was a split second of in game footage shown of Metroid Prime, and that's it. Why not more? Shiggy gave us the official word.
Today during the Shigeru round table Q&A he was asked why Metroid wasn't playable. He said he actually had more video in his backpack (laughs), but it wasn't up to his personal standards.
Shigeru also hinted at a late 2002 (if not 2003) release date.