I would have to disagree some what based on my discussion with Lars, who also was invited to benchmark Doom III on NV35.
Remember, that what you are looking at is still a pretty pre-release (alpha) build. The game still has not entered the Beta testing phase. Carmack himself has said many times that the targeted hardware for Doom III will be the Geforce 3/Radeon 8500 video card platforms. Basically, he said that a middle of the road configuration would be something close to an Xbox like PC.
Now, what does this mean? Well, the bottom line is that of course if you want all the eye candy and effects that are possible you will need a state of the art system with state of the art video performance. This of course is always going to be the bottom line.
Some of the statements that I have seen that indicate that you simply will not be able to play Doom III on older systems is simply false in my opinion. Until it is in Beta and the code has been set and the optimizations are all completed, I don't think anyone except Carmack really knows what kind of system that it will take to handle it.
I have said all along that I beleive that if you have at least a processor clocking 1.4GHz, 256MB of RAM, and a GeForce3/Radeon 8500 or higher you should be able to acheive a playable experience with Doom III.
In my opinion id would be foolish to release Doom III and make it playable only on the latest bleeding edge technology systems. Meaning 3GHz / 512MB / Radeon 9800/NV 35. From a pure marketing and money stand point, they would be cutting themselves off from so many people because they simply could not run the game. With the high development costs of Doom III, and the Doom III engine, they have to be able to sell the engine as well as the game to be used for a variety of other games in order to recoup their investment. While Carmack wants to bring the most state of the art engine out, he also realizes that they have to be able to make money too.
We will explore this question more in our meeting at E3 with the folks from Activision and see what they can tell us. I am sure that we will find out more at E3, but just from the money stand point, I can't see them cutting off that many sales, because users systems would not meet the reccomended system configuration.