Check out this small article from Computer Gaming World (.com) for a couple of John Carmack's random thoughts. Here's a snip:
Coding all by myself, there are fewer errors. But that's because I'd see and work on the engine by myself. For DOOM 3, we have five people working on it at the same time and problems are bound to come up -- and they aren't always easy to find. Between that and tightening up features for performance, it takes time. The most prudent thing at this point is to push through, fix the bugs and ship the game.
Not much covering Doom 3, but still an interesting (if not short) read. You may want to skip over CGW's sad attempt at humor intro, however.