Well keep in mind the game's presentation and production can have a tremendous effect on the overall feeling you get while playing it. I will definitely admit that some of the indoor segments do bear a striking resemblance to Doom 3 but I have a feeling that while it's in action we may not feel this way. Of course you can dismiss that as speculation if you wish, but some reviewers have said this as well. The reviews state clearly that the atmosphere of the game is different as well, and that the fast-paced action feel really sets the game apart from Doom. Heh, of course, it comes out in like 2 days so we'll know soon enough.