According to several interviews with Tim Willits, he said that the editor would be available by opening the console, typing "id studio" and pressing enter. Having just finished the game, I thought I'd take a look but the console command is unrecognised. How do you access the editor?
*UPDATE* doing a search for id studio showed me that its still forthcoming. Damn you id!
BTW, did anyone else notice that id spilled Doom 3 in my Rage? WTF was that final level?