Due to E3, natch, there's been quite a bit of new news and info and movies and screenshots about Doom 3 (or Doom^3 as it were) and Gamespot has once again come through with the goods (though you don't need to pay them and use their download util to get this) on a short Q&A session The Carmack gave. Here's a small snippit:
He didn't give any specific clues but said that it [the gamesave system] may be significantly different from what players are used to in previous id games. Given that in past games you were allowed to save anywhere, perhaps the company is considering a between-missions limitation for saving in the new game. When asked how long the game would be, Carmack wouldn't commit to a specific length but said that he favors the recent trend in the game industry toward shorter games with richer, deeper content packed into the duration.
There's also some stuff on disabling the real time shadows (for lower end machines) and how the id guys have gone about modeling some of the human characters in the game. It's a short, but informative read, and no doubt there will be more info spilled about Doom 3 before the expo ends.