The topics are his work on DOOM III and the future of gaming and hardware.
Behind the Scenes:
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.
You can find the full read and also a lot of new screenshots here and it's worth checking out.