I know there are many, many people are looking forward to Doom, and especially its editing capabilities, so when John Carmack speaks, we all listen! Interesting notes about the engine as quoted from two recent E3 interviews with the man:
"A big plus is that all of our tools are now built in to the game, so every release automatically has the tools that were used to build the game."
"Artists are going to have a significant learning curve to properly deal with the bump maps, but again, all the tools we use to generate them are included with the game."
"Level designers have to retrain themselves to use lighting more efficiently. Instead of plastering in hundreds of little lights to get your light maps the way you want, you need to think about primary key lights in a scene, and fill in around them as necessary. Cinematic lighting skills are now directly relevant."
"We offer full dynamic 5.1 channel sound mixing, and multichannel playback of studio sounds."
"This has been one of the areas where I know we are going to get some negative feedback. Doom III will only have minimal multiplayer facilities when released, because we are concentrating all of our efforts on making it an outstanding single-player experience ....... We will certainly be doing follow-up titles that refocus on multiplayer.'"
...and the best quote of all:
"Once you experience the consistency of the Doom world, other games start to feel more like puppet shows."
The two interviews are at gamespy and gamers.com...
Some links: first look at doom, E3 Doom impressions, more Doom3 details, some video, and the legacy trailer.