Well, I tried the Doom 3 alpha on a GF2mx and it didn't work. It would immediately hang at the initial window with a whole mess of flashing, red errors. This wasn't on my PC, though. Throwing their GF4ti back in there yielded perfect results.
I tried out a number of games that use similar effects to Doom 3, so if they are working in Doom 3...they are doing something impressive. Far Cry looked absolutely HORRIBLE on that card. All of the shiny surfaces and perpixel effects were just flat out GONE, the flashlight was f*cked, the texture surfaces just looked nasty, and all of the models looked screwy. Halo PC was even worse when running in DX7 mode. The textures were actually quite different and lacked the layering previously found in the game, the flashlight was awful looking, etc etc. Silent Hill 2 PC used a different flashlight effect (per-vertex lighting ala PS2).
How the hell did they pull off some of those effects in Doom 3? I mean, I've NEVER seen a DX7 card display the type of flashlight effect present in Doom 3. Your word isn't good enough, back it up. Based on the tests that I conducted, I am VERY skeptical that those effects will display properly on a GF2mx.
Obviously, those are DX games...so perhaps they are pulling those same effects off in a different fashion on OGL. However, despite whatever base they started with, I don't believe that the final product remains a DX7 engine...