While I agree that Doom3's engine is not all that impressive, I can't agree with this; "Yet they release an engine that cant be fully used for at least a year."
Look at the other major engine (Unreal), when UT2k3 came out, it needed a 256MB card to run it at full details. And by the way, DOOM3 can be ran at Ultra details assuming you have enough RAM, it's not because the game's programmed to select High detail when you have a 256MB card that the engine's unable to maintain a playable framerate (wich is subjective) at higher detail level.
As far as a slightly older post stating that Q3 had good bots. Please, it's not because just about every game as worst bots then Q3 that they can be qualified as good. They simply sucks. The first Unreal had better bots, and UT's one were ahead of them in so many way. They didn't even bother to include some in DOOM 3.
As far as I know, the current Unreal engine as more detailed level (polycount wise) and can make much bigger level. As far as directx9 tech, Source will be here soon. The only thing DOOM3's engine will be used for is other game with overly small level with your framerate cutting in half everytime you get in an outdoor level. And it's not surprising, RtCW (wich used to Q3 engine) was like that 3 years ago.