Gamespy published an interview with John Carmack. It talks about the engine, and some graphic cards. Bottom line there, according to Carmack: Radeon 8500 has the best features, and a nicer 'fragment path' and should be faster then the Gefore 4Ti, but the GF4Ti is faster in practice because of it's superior driver. Looks like he likes both enough to support them in Doom3, which is probably good.