http://www2.hardocp.com/article.html?art=NjQy
[H] OCP run some doom 3 benchmarks on Nvidia and Ati. Just some info on what kind of system you need. They seem to conclude that the engine is very flexible. How they come to this conclusion I don't know since they only test the top end cards (and gets abot 60fps on high qual, 1600 res, loads of AA). Interesting read but sounds like a bit of an attempt to get those, who were not willing to buy because they think they'll need an upgrade, to buy it.